part 1 - employer withdrawals

29 USC 1381 - Withdrawal liability established; criteria and definitions

(a) If an employer withdraws from a multiemployer plan in a complete withdrawal or a partial withdrawal, then the employer is liable to the plan in the amount determined under this part to be the withdrawal liability.
(b) For purposes of subsection (a) of this section
(1) The withdrawal liability of an employer to a plan is the amount determined under section 1391 of this title to be the allocable amount of unfunded vested benefits, adjusted
(A) first, by any de minimis reduction applicable under section 1389 of this title,
(B) next, in the case of a partial withdrawal, in accordance with section 1386 of this title,
(C) then, to the extent necessary to reflect the limitation on annual payments under section 1399 (c)(1)(B) of this title, and
(D) finally, in accordance with section 1405 of this title.
(2) The term complete withdrawal means a complete withdrawal described in section 1383 of this title.
(3) The term partial withdrawal means a partial withdrawal described in section 1385 of this title.

29 USC 1382 - Determination and collection of liability; notification of employer

When an employer withdraws from a multiemployer plan, the plan sponsor, in accordance with this part, shall
(1) determine the amount of the employers withdrawal liability,
(2) notify the employer of the amount of the withdrawal liability, and
(3) collect the amount of the withdrawal liability from the employer.

29 USC 1383 - Complete withdrawal

(a) Determinative factors 
For purposes of this part, a complete withdrawal from a multiemployer plan occurs when an employer
(1) permanently ceases to have an obligation to contribute under the plan, or
(2) permanently ceases all covered operations under the plan.
(b) Building and construction industry 

(1) Notwithstanding subsection (a) of this section, in the case of an employer that has an obligation to contribute under a plan for work performed in the building and construction industry, a complete withdrawal occurs only as described in paragraph (2), if
(A) substantially all the employees with respect to whom the employer has an obligation to contribute under the plan perform work in the building and construction industry, and
(B) the plan
(i) primarily covers employees in the building and construction industry, or
(ii) is amended to provide that this subsection applies to employers described in this paragraph.
(2) A withdrawal occurs under this paragraph if
(A) an employer ceases to have an obligation to contribute under the plan, and
(B) the employer
(i) continues to perform work in the jurisdiction of the collective bargaining agreement of the type for which contributions were previously required, or
(ii) resumes such work within 5 years after the date on which the obligation to contribute under the plan ceases, and does not renew the obligation at the time of the resumption.
(3) In the case of a plan terminated by mass withdrawal (within the meaning of section 1341a (a)(2) of this title), paragraph (2) shall be applied by substituting 3 years for 5 years in subparagraph (B)(ii).
(c) Entertainment industry 

(1) Notwithstanding subsection (a) of this section, in the case of an employer that has an obligation to contribute under a plan for work performed in the entertainment industry, primarily on a temporary or project-by-project basis, if the plan primarily covers employees in the entertainment industry, a complete withdrawal occurs only as described in subsection (b)(2) of this section applied by substituting plan for collective bargaining agreement in subparagraph (B)(i) thereof.
(2) For purposes of this subsection, the term entertainment industry means
(A) theater, motion picture (except to the extent provided in regulations prescribed by the corporation), radio, television, sound or visual recording, music, and dance, and
(B) such other entertainment activities as the corporation may determine to be appropriate.
(3) The corporation may by regulation exclude a group or class of employers described in the preceding sentence from the application of this subsection if the corporation determines that such exclusion is necessary
(A) to protect the interest of the plans participants and beneficiaries, or
(B) to prevent a significant risk of loss to the corporation with respect to the plan.
(4) A plan may be amended to provide that this subsection shall not apply to a group or class of employers under the plan.
(d) Other determinative factors 

(1) Notwithstanding subsection (a) of this section, in the case of an employer who
(A) has an obligation to contribute under a plan described in paragraph (2) primarily for work described in such paragraph, and
(B) does not continue to perform work within the jurisdiction of the plan,

a complete withdrawal occurs only as described in paragraph (3).

(2) A plan is described in this paragraph if substantially all of the contributions required under the plan are made by employers primarily engaged in the long and short haul trucking industry, the household goods moving industry, or the public warehousing industry.
(3) A withdrawal occurs under this paragraph if
(A) an employer permanently ceases to have an obligation to contribute under the plan or permanently ceases all covered operations under the plan, and
(B) either
(i) the corporation determines that the plan has suffered substantial damage to its contribution base as a result of such cessation, or
(ii) the employer fails to furnish a bond issued by a corporate surety company that is an acceptable surety for purposes of section 1112 of this title, or an amount held in escrow by a bank or similar financial institution satisfactory to the plan, in an amount equal to 50 percent of the withdrawal liability of the employer.
(4) If, after an employer furnishes a bond or escrow to a plan under paragraph (3)(B)(ii), the corporation determines that the cessation of the employers obligation to contribute under the plan (considered together with any cessations by other employers), or cessation of covered operations under the plan, has resulted in substantial damage to the contribution base of the plan, the employer shall be treated as having withdrawn from the plan on the date on which the obligation to contribute or covered operations ceased, and such bond or escrow shall be paid to the plan. The corporation shall not make a determination under this paragraph more than 60 months after the date on which such obligation to contribute or covered operations ceased.
(5) If the corporation determines that the employer has no further liability under the plan either
(A) because it determines that the contribution base of the plan has not suffered substantial damage as a result of the cessation of the employers obligation to contribute or cessation of covered operations (considered together with any cessation of contribution obligation, or of covered operations, with respect to other employers), or
(B) because it may not make a determination under paragraph (4) because of the last sentence thereof,

then the bond shall be cancelled or the escrow refunded.

(6) Nothing in this subsection shall be construed as a limitation on the amount of the withdrawal liability of any employer.
(e) Date of complete withdrawal 
For purposes of this part, the date of a complete withdrawal is the date of the cessation of the obligation to contribute or the cessation of covered operations.
(f) Special liability withdrawal rules for industries other than construction and entertainment industries; procedures applicable to amend plans 

(1) The corporation may prescribe regulations under which plans in industries other than the construction or entertainment industries may be amended to provide for special withdrawal liability rules similar to the rules described in subsections (b) and (c) of this section.
(2) Regulations under paragraph (1) shall permit use of special withdrawal liability rules
(A) only in industries (or portions thereof) in which, as determined by the corporation, the characteristics that would make use of such rules appropriate are clearly shown, and
(B) only if the corporation determines, in each instance in which special withdrawal liability rules are permitted, that use of such rules will not pose a significant risk to the corporation under this subchapter.

29 USC 1384 - Sale of assets

(a) Complete or partial withdrawal not occurring as a result of sale and subsequent cessation of covered operations or cessation of obligation to contribute to covered operations; continuation of liability of seller 

(1) A complete or partial withdrawal of an employer (hereinafter in this section referred to as the seller) under this section does not occur solely because, as a result of a bona fide, arms-length sale of assets to an unrelated party (hereinafter in this section referred to as the purchaser), the seller ceases covered operations or ceases to have an obligation to contribute for such operations, if
(A) the purchaser has an obligation to contribute to the plan with respect to the operations for substantially the same number of contribution base units for which the seller had an obligation to contribute to the plan;
(B) the purchaser provides to the plan for a period of 5 plan years commencing with the first plan year beginning after the sale of assets, a bond issued by a corporate surety company that is an acceptable surety for purposes of section 1112 of this title, or an amount held in escrow by a bank or similar financial institution satisfactory to the plan, in an amount equal to the greater of
(i) the average annual contribution required to be made by the seller with respect to the operations under the plan for the 3 plan years preceding the plan year in which the sale of the employers assets occurs, or
(ii) the annual contribution that the seller was required to make with respect to the operations under the plan for the last plan year before the plan year in which the sale of the assets occurs,

which bond or escrow shall be paid to the plan if the purchaser withdraws from the plan, or fails to make a contribution to the plan when due, at any time during the first 5 plan years beginning after the sale; and

(C) the contract for sale provides that, if the purchaser withdraws in a complete withdrawal, or a partial withdrawal with respect to operations, during such first 5 plan years, the seller is secondarily liable for any withdrawal liability it would have had to the plan with respect to the operations (but for this section) if the liability of the purchaser with respect to the plan is not paid.
(2) If the purchaser
(A) withdraws before the last day of the fifth plan year beginning after the sale, and
(B) fails to make any withdrawal liability payment when due,

then the seller shall pay to the plan an amount equal to the payment that would have been due from the seller but for this section.

(3) 
(A) If all, or substantially all, of the sellers assets are distributed, or if the seller is liquidated before the end of the 5 plan year period described in paragraph (1)(C), then the seller shall provide a bond or amount in escrow equal to the present value of the withdrawal liability the seller would have had but for this subsection.
(B) If only a portion of the sellers assets are distributed during such period, then a bond or escrow shall be required, in accordance with regulations prescribed by the corporation, in a manner consistent with subparagraph (A).
(4) The liability of the party furnishing a bond or escrow under this subsection shall be reduced, upon payment of the bond or escrow to the plan, by the amount thereof.
(b) Liability of purchaser 

(1) For the purposes of this part, the liability of the purchaser shall be determined as if the purchaser had been required to contribute to the plan in the year of the sale and the 4 plan years preceding the sale the amount the seller was required to contribute for such operations for such 5 plan years.
(2) If the plan is in reorganization in the plan year in which the sale of assets occurs, the purchaser shall furnish a bond or escrow in an amount equal to 200 percent of the amount described in subsection (a)(1)(B) of this section.
(c) Variances or exemptions from continuation of liability of seller; procedures applicable 
The corporation may by regulation vary the standards in subparagraphs (B) and (C) of subsection (a)(1) of this section if the variance would more effectively or equitably carry out the purposes of this subchapter. Before it promulgates such regulations, the corporation may grant individual or class variances or exemptions from the requirements of such subparagraphs if the particular case warrants it. Before granting such an individual or class variance or exemption, the corporation
(1) shall publish notice in the Federal Register of the pendency of the variance or exemption,
(2) shall require that adequate notice be given to interested persons, and
(3) shall afford interested persons an opportunity to present their views.
(d) “Unrelated party” defined 
For purposes of this section, the term unrelated party means a purchaser or seller who does not bear a relationship to the seller or purchaser, as the case may be, that is described in section 267 (b) of title 26, or that is described in regulations prescribed by the corporation applying principles similar to the principles of such section.

29 USC 1385 - Partial withdrawals

(a) Determinative factors 
Except as otherwise provided in this section, there is a partial withdrawal by an employer from a plan on the last day of a plan year if for such plan year
(1) there is a 70-percent contribution decline, or
(2) there is a partial cessation of the employers contribution obligation.
(b) Criteria applicable 
For purposes of subsection (a) of this section
(1) 
(A) There is a 70-percent contribution decline for any plan year if during each plan year in the 3-year testing period the employers contribution base units do not exceed 30 percent of the employers contribution base units for the high base year.
(B) For purposes of subparagraph (A)
(i) The term 3-year testing period means the period consisting of the plan year and the immediately preceding 2 plan years.
(ii) The number of contribution base units for the high base year is the average number of such units for the 2 plan years for which the employers contribution base units were the highest within the 5 plan years immediately preceding the beginning of the 3-year testing period.
(2) 
(A) There is a partial cessation of the employers contribution obligation for the plan year if, during such year
(i) the employer permanently ceases to have an obligation to contribute under one or more but fewer than all collective bargaining agreements under which the employer has been obligated to contribute under the plan but continues to perform work in the jurisdiction of the collective bargaining agreement of the type for which contributions were previously required or transfers such work to another location or to an entity or entities owned or controlled by the employer, or
(ii) an employer permanently ceases to have an obligation to contribute under the plan with respect to work performed at one or more but fewer than all of its facilities, but continues to perform work at the facility of the type for which the obligation to contribute ceased.
(B) For purposes of subparagraph (A), a cessation of obligations under a collective bargaining agreement shall not be considered to have occurred solely because, with respect to the same plan, one agreement that requires contributions to the plan has been substituted for another agreement.
(c) Retail food industry 

(1) In the case of a plan in which a majority of the covered employees are employed in the retail food industry, the plan may be amended to provide that this section shall be applied with respect to such plan
(A) by substituting 35 percent for 70 percent in subsections (a) and (b) of this section, and
(B) by substituting 65 percent for 30 percent in subsection (b) of this section.
(2) Any amendment adopted under paragraph (1) shall provide rules for the equitable reduction of withdrawal liability in any case in which the number of the plans contribution base units, in the 2 plan years following the plan year of withdrawal of the employer, is higher than such number immediately after the withdrawal.
(3) Section 1388 of this title shall not apply to a plan which has been amended under paragraph (1).
(d) Continuation of liability of employer for partial withdrawal under amended plan 
In the case of a plan described in section 404 (c) of title 26, or a continuation thereof, the plan may be amended to provide rules setting forth other conditions consistent with the purposes of this chapter under which an employer has liability for partial withdrawal.

29 USC 1386 - Adjustment for partial withdrawal; determination of amount; reduction for partial withdrawal liability; procedures applicable

(a) The amount of an employers liability for a partial withdrawal, before the application of sections 1399 (c)(1) and 1405 of this title, is equal to the product of
(1) the amount determined under section 1391 of this title, and adjusted under section 1389 of this title if appropriate, determined as if the employer had withdrawn from the plan in a complete withdrawal
(A) on the date of the partial withdrawal, or
(B) in the case of a partial withdrawal described in section 1385 (a)(1) of this title (relating to 70-percent contribution decline), on the last day of the first plan year in the 3-year testing period,

multiplied by

(2) a fraction which is 1 minus a fraction
(A) the numerator of which is the employers contribution base units for the plan year following the plan year in which the partial withdrawal occurs, and
(B) the denominator of which is the average of the employers contribution base units for
(i) except as provided in clause (ii), the 5 plan years immediately preceding the plan year in which the partial withdrawal occurs, or
(ii) in the case of a partial withdrawal described in section 1385 (a)(1) of this title (relating to 70-percent contribution decline), the 5 plan years immediately preceding the beginning of the 3-year testing period.
(b) 
(1) In the case of an employer that has withdrawal liability for a partial withdrawal from a plan, any withdrawal liability of that employer for a partial or complete withdrawal from that plan in a subsequent plan year shall be reduced by the amount of any partial withdrawal liability (reduced by any abatement or reduction of such liability) of the employer with respect to the plan for a previous plan year.
(2) The corporation shall prescribe such regulations as may be necessary to provide for proper adjustments in the reduction provided by paragraph (1) for
(A) changes in unfunded vested benefits arising after the close of the prior year for which partial withdrawal liability was determined,
(B) changes in contribution base units occurring after the close of the prior year for which partial withdrawal liability was determined, and
(C) any other factors for which it determines adjustment to be appropriate,

so that the liability for any complete or partial withdrawal in any subsequent year (after the application of the reduction) properly reflects the employers share of liability with respect to the plan.

29 USC 1387 - Reduction or waiver of complete withdrawal liability; procedures and standards applicable

(a) The corporation shall provide by regulation for the reduction or waiver of liability for a complete withdrawal in the event that an employer who has withdrawn from a plan subsequently resumes covered operations under the plan or renews an obligation to contribute under the plan, to the extent that the corporation determines that reduction or waiver of withdrawal liability is consistent with the purposes of this chapter.
(b) The corporation shall prescribe by regulation a procedure and standards for the amendment of plans to provide alternative rules for the reduction or waiver of liability for a complete withdrawal in the event that an employer who has withdrawn from the plan subsequently resumes covered operations or renews an obligation to contribute under the plan. The rules may apply only to the extent that the rules are consistent with the purposes of this chapter.

29 USC 1388 - Reduction of partial withdrawal liability

(a) Obligation of employer for payments for partial withdrawal for plan years beginning after the second consecutive plan year following the partial withdrawal year; criteria applicable; furnishing of bond in lieu of payment of partial withdrawal liability 

(1) If, for any 2 consecutive plan years following the plan year in which an employer has partially withdrawn from a plan under section 1385 (a)(1) of this title (referred to elsewhere in this section as the partial withdrawal year), the number of contribution base units with respect to which the employer has an obligation to contribute under the plan for each such year is not less than 90 percent of the total number of contribution base units with respect to which the employer had an obligation to contribute under the plan for the high base year (within the meaning of section 1385 (b)(1)(B)(ii) of this title), then the employer shall have no obligation to make payments with respect to such partial withdrawal (other than delinquent payments) for plan years beginning after the second consecutive plan year following the partial withdrawal year.
(2) 
(A) For any plan year for which the number of contribution base units with respect to which an employer who has partially withdrawn under section 1385 (a)(1) of this title has an obligation to contribute under the plan equals or exceeds the number of units for the highest year determined under paragraph (1) without regard to 90 percent of, the employer may furnish (in lieu of payment of the partial withdrawal liability determined under section 1386 of this title) a bond to the plan in the amount determined by the plan sponsor (not exceeding 50 percent of the annual payment otherwise required).
(B) If the plan sponsor determines under paragraph (1) that the employer has no further liability to the plan for the partial withdrawal, then the bond shall be cancelled.
(C) If the plan sponsor determines under paragraph (1) that the employer continues to have liability to the plan for the partial withdrawal, then
(i) the bond shall be paid to the plan,
(ii) the employer shall immediately be liable for the outstanding amount of liability due with respect to the plan year for which the bond was posted, and
(iii) the employer shall continue to make the partial withdrawal liability payments as they are due.
(b) Obligation of employer for payments for partial withdrawal for plan years beginning after the second consecutive plan year; other criteria applicable 
If
(1) for any 2 consecutive plan years following a partial withdrawal under section 1385 (a)(1) of this title, the number of contribution base units with respect to which the employer has an obligation to contribute for each such year exceeds 30 percent of the total number of contribution base units with respect to which the employer had an obligation to contribute for the high base year (within the meaning of section 1385 (b)(1)(B)(ii) of this title,[1] and
(2) the total number of contribution base units with respect to which all employers under the plan have obligations to contribute in each of such 2 consecutive years is not less than 90 percent of the total number of contribution base units for which all employers had obligations to contribute in the partial withdrawal plan year;

then, the employer shall have no obligation to make payments with respect to such partial withdrawal (other than delinquent payments) for plan years beginning after the second such consecutive plan year.

(c) Pro rata reduction of amount of partial withdrawal liability payment of employer for plan year following partial withdrawal year 
In any case in which, in any plan year following a partial withdrawal under section 1385 (a)(1) of this title, the number of contribution base units with respect to which the employer has an obligation to contribute for such year equals or exceeds 110 percent (or such other percentage as the plan may provide by amendment and which is not prohibited under regulations prescribed by the corporation) of the number of contribution base units with respect to which the employer had an obligation to contribute in the partial withdrawal year, then the amount of the employers partial withdrawal liability payment for such year shall be reduced pro rata, in accordance with regulations prescribed by the corporation.
(d) Building and construction industry; entertainment industry 

(1) An employer to whom section 1383 (b)2 of this title (relating to the building and construction industry) applies is liable for a partial withdrawal only if the employers obligation to contribute under the plan is continued for no more than an insubstantial portion of its work in the craft and area jurisdiction of the collective bargaining agreement of the type for which contributions are required.
(2) An employer to whom section 1383 (c)2 of this title (relating to the entertainment industry) applies shall have no liability for a partial withdrawal except under the conditions and to the extent prescribed by the corporation by regulation.
(e) Reduction or elimination of partial withdrawal liability under any conditions; criteria; procedures applicable 

(1) The corporation may prescribe regulations providing for the reduction or elimination of partial withdrawal liability under any conditions with respect to which the corporation determines that reduction or elimination of partial withdrawal liability is consistent with the purposes of this chapter.
(2) Under such regulations, reduction of withdrawal liability shall be provided only with respect to subsequent changes in the employers contributions for the same operations, or under the same collective bargaining agreement, that gave rise to the partial withdrawal, and changes in the employers contribution base units with respect to other facilities or other collective bargaining agreements shall not be taken into account.
(3) The corporation shall prescribe by regulation a procedure by which a plan may by amendment adopt rules for the reduction or elimination of partial withdrawal liability under any other conditions, subject to the approval of the corporation based on its determination that adoption of such rules by the plan is consistent with the purposes of this chapter.
[1] So in original. Probably should be “title),”.
[2] See References in Text note below.

29 USC 1389 - De minimis rule

(a) Reduction of unfunded vested benefits allocable to employer withdrawn from plan 
Except in the case of a plan amended under subsection (b) of this section, the amount of the unfunded vested benefits allocable under section 1391 of this title to an employer who withdraws from a plan shall be reduced by the smaller of
(1) 3/4 of 1 percent of the plans unfunded vested obligations (determined as of the end of the plan year ending before the date of withdrawal), or
(2) $50,000,

reduced by the amount, if any, by which the unfunded vested benefits allowable to the employer, determined without regard to this subsection, exceeds $100,000.

(b) Amendment of plan for reduction of amount of unfunded vested benefits allocable to employer withdrawn from plan 
A plan may be amended to provide for the reduction of the amount determined under section 1391 of this title by not more than the greater of
(1) the amount determined under subsection (a) of this section, or
(2) the lesser of
(A) the amount determined under subsection (a)(1) of this section, or
(B) $100,000,

reduced by the amount, if any, by which the amount determined under section 1391 of this title for the employer, determined without regard to this subsection, exceeds $150,000.

(c) Nonapplicability 
This section does not apply
(1) to an employer who withdraws in a plan year in which substantially all employers withdraw from the plan, or
(2) in any case in which substantially all employers withdraw from the plan during a period of one or more plan years pursuant to an agreement or arrangement to withdraw, to an employer who withdraws pursuant to such agreement or arrangement.
(d) Presumption of employer withdrawal from plan pursuant to agreement or arrangement applicable in action or proceeding to determine or collect withdrawal liability 
In any action or proceeding to determine or collect withdrawal liability, if substantially all employers have withdrawn from a plan within a period of 3 plan years, an employer who has withdrawn from such plan during such period shall be presumed to have withdrawn from the plan pursuant to an agreement or arrangement, unless the employer proves otherwise by a preponderance of the evidence.

29 USC 1390 - Nonapplicability of withdrawal liability for certain temporary contribution obligation periods; exception

(a) An employer who withdraws from a plan in complete or partial withdrawal is not liable to the plan if the employer
(1) first had an obligation to contribute to the plan after September 26, 1980,
(2) had an obligation to contribute to the plan for no more than the lesser of
(A) 6 consecutive plan years preceding the date on which the employer withdraws, or
(B) the number of years required for vesting under the plan,
(3) was required to make contributions to the plan for each such plan year in an amount equal to less than 2 percent of the sum of all employer contributions made to the plan for each such year, and
(4) has never avoided withdrawal liability because of the application of this section with respect to the plan.
(b) Subsection (a) of this section shall apply to an employer with respect to a plan only if
(1) the plan is amended to provide that subsection (a) of this section applies;
(2) the plan provides, or is amended to provide, that the reduction under section 411 (a)(3)(E) of title 26 applies with respect to the employees of the employer; and
(3) the ratio of the assets of the plan for the plan year preceding the first plan year for which the employer was required to contribute to the plan to the benefit payments made during that plan year was at least 8 to 1.

29 USC 1391 - Methods for computing withdrawal liability

(a) Determination of amount of unfunded vested benefits allocable to employer withdrawn from plan 
The amount of the unfunded vested benefits allocable to an employer that withdraws from a plan shall be determined in accordance with subsection (b), (c), or (d) of this section.
(b) Factors determining computation of amount of unfunded vested benefits allocable to employer withdrawn from plan 

(1) Except as provided in subsections (c) and (d) of this section, the amount of unfunded vested benefits allocable to an employer that withdraws is the sum of
(A) the employers proportional share of the unamortized amount of the change in the plans unfunded vested benefits for plan years ending after September 25, 1980, as determined under paragraph (2),
(B) the employers proportional share, if any, of the unamortized amount of the plans unfunded vested benefits at the end of the plan year ending before September 26, 1980, as determined under paragraph (3); and
(C) the employers proportional share of the unamortized amounts of the reallocated unfunded vested benefits (if any) as determined under paragraph (4).

If the sum of the amounts determined with respect to an employer under paragraphs (2), (3), and (4) is negative, the unfunded vested benefits allocable to the employer shall be zero.

(2) 
(A) An employers proportional share of the unamortized amount of the change in the plans unfunded vested benefits for plan years ending after September 25, 1980, is the sum of the employers proportional shares of the unamortized amount of the change in unfunded vested benefits for each plan year in which the employer has an obligation to contribute under the plan ending
(i) after such date, and
(ii) before the plan year in which the withdrawal of the employer occurs.
(B) The change in a plans unfunded vested benefits for a plan year is the amount by which
(i) the unfunded vested benefits at the end of the plan year; exceeds
(ii) the sum of
(I) the unamortized amount of the unfunded vested benefits for the last plan year ending before September 26, 1980, and
(II) the sum of the unamortized amounts of the change in unfunded vested benefits for each plan year ending after September 25, 1980, and preceding the plan year for which the change is determined.
(C) The unamortized amount of the change in a plans unfunded vested benefits with respect to a plan year is the change in unfunded vested benefits for the plan year, reduced by 5 percent of such change for each succeeding plan year.
(D) The unamortized amount of the unfunded vested benefits for the last plan year ending before September 26, 1980, is the amount of the unfunded vested benefits as of the end of that plan year reduced by 5 percent of such amount for each succeeding plan year.
(E) An employers proportional share of the unamortized amount of a change in unfunded vested benefits is the product of
(i) the unamortized amount of such change (as of the end of the plan year preceding the plan year in which the employer withdraws); multiplied by
(ii) a fraction
(I) the numerator of which is the sum of the contributions required to be made under the plan by the employer for the year in which such change arose and for the 4 preceding plan years, and
(II) the denominator of which is the sum for the plan year in which such change arose and the 4 preceding plan years of all contributions made by employers who had an obligation to contribute under the plan for the plan year in which such change arose reduced by the contributions made in such years by employers who had withdrawn from the plan in the year in which the change arose.
(3) An employers proportional share of the unamortized amount of the plans unfunded vested benefits for the last plan year ending before September 26, 1980, is the product of
(A) such unamortized amount; multiplied by
(B) a fraction
(i) the numerator of which is the sum of all contributions required to be made by the employer under the plan for the most recent 5 plan years ending before September 26, 1980, and
(ii) the denominator of which is the sum of all contributions made for the most recent 5 plan years ending before September 26, 1980, by all employers
(I) who had an obligation to contribute under the plan for the first plan year ending on or after such date, and
(II) who had not withdrawn from the plan before such date.
(4) 
(A) An employers proportional share of the unamortized amount of the reallocated unfunded vested benefits is the sum of the employers proportional share of the unamortized amount of the reallocated unfunded vested benefits for each plan year ending before the plan year in which the employer withdrew from the plan.
(B) Except as otherwise provided in regulations prescribed by the corporation, the reallocated unfunded vested benefits for a plan year is the sum of
(i) any amount which the plan sponsor determines in that plan year to be uncollectible for reasons arising out of cases or proceedings under title 11, or similar proceedings.[1]
(ii) any amount which the plan sponsor determines in that plan year will not be assessed as a result of the operation of section 1389, 1399 (c)(1)(B), or 1405 of this title against an employer to whom a notice described in section 1399 of this title has been sent, and
(iii) any amount which the plan sponsor determines to be uncollectible or unassessable in that plan year for other reasons under standards not inconsistent with regulations prescribed by the corporation.
(C) The unamortized amount of the reallocated unfunded vested benefits with respect to a plan year is the reallocated unfunded vested benefits for the plan year, reduced by 5 percent of such reallocated unfunded vested benefits for each succeeding plan year.
(D) An employers proportional share of the unamortized amount of the reallocated unfunded vested benefits with respect to a plan year is the product of
(i) the unamortized amount of the reallocated unfunded vested benefits (as of the end of the plan year preceding the plan year in which the employer withdraws); multiplied by
(ii) the fraction defined in paragraph (2)(E)(ii).
(c) Amendment of multiemployer plan for determination respecting amount of unfunded vested benefits allocable to employer withdrawn from plan; factors determining computation of amount 

(1) A multiemployer plan, other than a plan which primarily covers employees in the building and construction industry, may be amended to provide that the amount of unfunded vested benefits allocable to an employer that withdraws from the plan is an amount determined under paragraph (2), (3), (4), or (5) of this subsection, rather than under subsection (b) or (d) of this section. A plan described in section 1383 (b)(1)(B)(i) of this title (relating to the building and construction industry) may be amended, to the extent provided in regulations prescribed by the corporation, to provide that the amount of the unfunded vested benefits allocable to an employer not described in section 1383 (b)(1)(A) of this title shall be determined in a manner different from that provided in subsection (b) of this section.
(2) 
(A) The amount of the unfunded vested benefits allocable to any employer under this paragraph is the sum of the amounts determined under subparagraphs (B) and (C).
(B) The amount determined under this subparagraph is the product of
(i) the plans unfunded vested benefits as of the end of the last plan year ending before September 26, 1980, reduced as if those obligations were being fully amortized in level annual installments over 15 years beginning with the first plan year ending on or after such date; multiplied by
(ii) a fraction
(I) the numerator of which is the sum of all contributions required to be made by the employer under the plan for the last 5 plan years ending before September 26, 1980, and
(II) the denominator of which is the sum of all contributions made for the last 5 plan years ending before September 26, 1980, by all employers who had an obligation to contribute under the plan for the first plan year ending after September 25, 1980, and who had not withdrawn from the plan before such date.
(C) The amount determined under this subparagraph is the product of
(i) an amount equal to
(I) the plans unfunded vested benefits as of the end of the plan year preceding the plan year in which the employer withdraws, less
(II) the sum of the value as of such date of all outstanding claims for withdrawal liability which can reasonably be expected to be collected, with respect to employers withdrawing before such plan year, and that portion of the amount determined under subparagraph (B)(i) which is allocable to employers who have an obligation to contribute under the plan in the plan year preceding the plan year in which the employer withdraws and who also had an obligation to contribute under the plan for the first plan year ending after September 25, 1980; multiplied by
(ii) a fraction
(I) the numerator of which is the total amount required to be contributed under the plan by the employer for the last 5 plan years ending before the date on which the employer withdraws, and
(II) the denominator of which is the total amount contributed under the plan by all employers for the last 5 plan years ending before the date on which the employer withdraws, increased by the amount of any employer contributions owed with respect to earlier periods which were collected in those plan years, and decreased by any amount contributed by an employer who withdrew from the plan under this part during those plan years.
(D) The corporation may by regulation permit adjustments in any denominator under this section, consistent with the purposes of this subchapter, where such adjustment would be appropriate to ease administrative burdens of plan sponsors in calculating such denominators.
(3) The amount of the unfunded vested benefits allocable to an employer under this paragraph is the product of
(A) the plans unfunded vested benefits as of the end of the plan year preceding the plan year in which the employer withdraws, less the value as of the end of such year of all outstanding claims for withdrawal liability which can reasonably be expected to be collected from employers withdrawing before such year; multiplied by
(B) a fraction
(i) the numerator of which is the total amount required to be contributed by the employer under the plan for the last 5 plan years ending before the withdrawal, and
(ii) the denominator of which is the total amount contributed under the plan by all employers for the last 5 plan years ending before the withdrawal, increased by any employer contributions owed with respect to earlier periods which were collected in those plan years, and decreased by any amount contributed to the plan during those plan years by employers who withdrew from the plan under this section during those plan years.
(4) 
(A) The amount of the unfunded vested benefits allocable to an employer under this paragraph is equal to the sum of
(i) the plans unfunded vested benefits which are attributable to participants service with the employer (determined as of the end of the plan year preceding the plan year in which the employer withdraws), and
(ii) the employers proportional share of any unfunded vested benefits which are not attributable to service with the employer or other employers who are obligated to contribute under the plan in the plan year preceding the plan year in which the employer withdraws (determined as of the end of the plan year preceding the plan year in which the employer withdraws).
(B) The plans unfunded vested benefits which are attributable to participants service with the employer is the amount equal to the value of nonforfeitable benefits under the plan which are attributable to participants service with such employer (determined under plan rules not inconsistent with regulations of the corporation) decreased by the share of plan assets determined under subparagraph (C) which is allocated to the employer as provided under subparagraph (D).
(C) The value of plan assets determined under this subparagraph is the value of plan assets allocated to nonforfeitable benefits which are attributable to service with the employers who have an obligation to contribute under the plan in the plan year preceding the plan year in which the employer withdraws, which is determined by multiplying
(i) the value of the plan assets as of the end of the plan year preceding the plan year in which the employer withdraws, by
(ii) a fraction
(I) the numerator of which is the value of nonforfeitable benefits which are attributable to service with such employers, and
(II) the denominator of which is the value of all nonforfeitable benefits under the plan as of the end of the plan year.
(D) The share of plan assets, determined under subparagraph (C), which is allocated to the employer shall be determined in accordance with one of the following methods which shall be adopted by the plan by amendment:
(i) by multiplying the value of plan assets determined under subparagraph (C) by a fraction
(I) the numerator of which is the value of the nonforfeitable benefits which are attributable to service with the employer, and
(II) the denominator of which is the value of the nonforfeitable benefits which are attributable to service with all employers who have an obligation to contribute under the plan in the plan year preceding the plan year in which the employer withdraws;
(ii) by multiplying the value of plan assets determined under subparagraph (C) by a fraction
(I) the numerator of which is the sum of all contributions (accumulated with interest) which have been made to the plan by the employer for the plan year preceding the plan year in which the employer withdraws and all preceding plan years; and
(II) the denominator of which is the sum of all contributions (accumulated with interest) which have been made to the plan (for the plan year preceding the plan year in which the employer withdraws and all preceding plan years) by all employers who have an obligation to contribute to the plan for the plan year preceding the plan year in which the employer withdraws; or
(iii) by multiplying the value of plan assets under subparagraph (C) by a fraction
(I) the numerator of which is the amount determined under clause (ii)(I) of this subparagraph, less the sum of benefit payments (accumulated with interest) made to participants (and their beneficiaries) for the plan years described in such clause (ii)(I) which are attributable to service with the employer; and
(II) the denominator of which is the amount determined under clause (ii)(II) of this subparagraph, reduced by the sum of benefit payments (accumulated with interest) made to participants (and their beneficiaries) for the plan years described in such clause (ii)(II) which are attributable to service with respect to the employers described in such clause (ii)(II).
(E) The amount of the plans unfunded vested benefits for a plan year preceding the plan year in which an employer withdraws, which is not attributable to service with employers who have an obligation to contribute under the plan in the plan year preceding the plan year in which such employer withdraws, is equal to
(i) an amount equal to
(I) the value of all nonforfeitable benefits under the plan at the end of such plan year, reduced by
(II) the value of nonforfeitable benefits under the plan at the end of such plan year which are attributable to participants service with employers who have an obligation to contribute under the plan for such plan year; reduced by
(ii) an amount equal to
(I) the value of the plan assets as of the end of such plan year, reduced by
(II) the value of plan assets as of the end of such plan year as determined under subparagraph (C); reduced by
(iii) the value of all outstanding claims for withdrawal liability which can reasonably be expected to be collected with respect to employers withdrawing before the year preceding the plan year in which the employer withdraws.
(F) The employers proportional share described in subparagraph (A)(ii) for a plan year is the amount determined under subparagraph (E) for the employer, but not in excess of an amount which bears the same ratio to the sum of the amounts determined under subparagraph (E) for all employers under the plan as the amount determined under subparagraph (C) for the employer bears to the sum of the amounts determined under subparagraph (C) for all employers under the plan.
(G) The corporation may prescribe by regulation other methods which a plan may adopt for allocating assets to determine the amount of the unfunded vested benefits attributable to service with the employer and to determine the employers share of unfunded vested benefits not attributable to service with employers who have an obligation to contribute under the plan in the plan year in which the employer withdraws.
(5) 
(A) The corporation shall prescribe by regulation a procedure by which a plan may, by amendment, adopt any other alternative method for determining an employers allocable share of unfunded vested benefits under this section, subject to the approval of the corporation based on its determination that adoption of the method by the plan would not significantly increase the risk of loss to plan participants and beneficiaries or to the corporation.
(B) The corporation may prescribe by regulation standard approaches for alternative methods, other than those set forth in the preceding paragraphs of this subsection, which a plan may adopt under subparagraph (A), for which the corporation may waive or modify the approval requirements of subparagraph (A). Any alternative method shall provide for the allocation of substantially all of a plans unfunded vested benefits among employers who have an obligation to contribute under the plan.
(C) Unless the corporation by regulation provides otherwise, a plan may be amended to provide that a period of more than 5 but not more than 10 plan years may be used for determining the numerator and denominator of any fraction which is used under any method authorized under this section for determining an employers allocable share of unfunded vested benefits under this section.
(D) The corporation may by regulation permit adjustments in any denominator under this section, consistent with the purposes of this subchapter, where such adjustment would be appropriate to ease administrative burdens of plan sponsors in calculating such denominators.
(E) Fresh start option.— 
Notwithstanding paragraph (1), a plan may be amended to provide that the withdrawal liability method described in subsection (b) shall be applied by substituting the plan year which is specified in the amendment and for which the plan has no unfunded vested benefits for the plan year ending before September 26, 1980.
(d) Method of calculating allocable share of employer of unfunded vested benefits set forth in subsection (c)(3) of this section; applicability of certain statutory provisions 

(1) The method of calculating an employers allocable share of unfunded vested benefits set forth in subsection (c)(3) of this section shall be the method for calculating an employers allocable share of unfunded vested benefits under a plan to which section 404 (c) of title 26, or a continuation of such a plan, applies, unless the plan is amended to adopt another method authorized under subsection (b) or (c) of this section.
(2) Sections 1384, 1389, 1399 (c)(1)(B), and 1405 of this title shall not apply with respect to the withdrawal of an employer from a plan described in paragraph (1) unless the plan is amended to provide that any of such sections apply.
(e) Reduction of liability of withdrawn employer in case of transfer of liabilities to another plan incident to withdrawal or partial withdrawal of employer 
In the case of a transfer of liabilities to another plan incident to an employers withdrawal or partial withdrawal, the withdrawn employers liability under this part shall be reduced in an amount equal to the value, as of the end of the last plan year ending on or before the date of the withdrawal, of the transferred unfunded vested benefits.
(f) Computations applicable in case of withdrawal following merger of multiemployer plans 
In the case of a withdrawal following a merger of multiemployer plans, subsection (b), (c), or (d) of this section shall be applied in accordance with regulations prescribed by the corporation; except that, if a withdrawal occurs in the first plan year beginning after a merger of multiemployer plans, the determination under this section shall be made as if each of the multiemployer plans had remained separate plans.
[1] So in original. The period probably should be a comma.

29 USC 1392 - Obligation to contribute

(a) “Obligation to contribute” defined 
For purposes of this part, the term obligation to contribute means an obligation to contribute arising
(1) under one or more collective bargaining (or related) agreements, or
(2) as a result of a duty under applicable labor-management relations law, but

does not include an obligation to pay withdrawal liability under this section or to pay delinquent contributions.

(b) Payments of withdrawal liability not considered contributions 
Payments of withdrawal liability under this part shall not be considered contributions for purposes of this part.
(c) Transactions to evade or avoid liability 
If a principal purpose of any transaction is to evade or avoid liability under this part, this part shall be applied (and liability shall be determined and collected) without regard to such transaction.

29 USC 1393 - Actuarial assumptions

(a) Use by plan actuary in determining unfunded vested benefits of a plan for computing withdrawal liability of employer 
The corporation may prescribe by regulation actuarial assumptions which may be used by a plan actuary in determining the unfunded vested benefits of a plan for purposes of determining an employers withdrawal liability under this part. Withdrawal liability under this part shall be determined by each plan on the basis of
(1) actuarial assumptions and methods which, in the aggregate, are reasonable (taking into account the experience of the plan and reasonable expectations) and which, in combination, offer the actuarys best estimate of anticipated experience under the plan, or
(2) actuarial assumptions and methods set forth in the corporations regulations for purposes of determining an employers withdrawal liability.
(b) Factors determinative of unfunded vested benefits of plan for computing withdrawal liability of employer 
In determining the unfunded vested benefits of a plan for purposes of determining an employers withdrawal liability under this part, the plan actuary may
(1) rely on the most recent complete actuarial valuation used for purposes of section 412 of title 26 and reasonable estimates for the interim years of the unfunded vested benefits, and
(2) in the absence of complete data, rely on the data available or on data secured by a sampling which can reasonably be expected to be representative of the status of the entire plan.
(c) Determination of amount of unfunded vested benefits 
For purposes of this part, the term unfunded vested benefits means with respect to a plan, an amount equal to
(A) the value of nonforfeitable benefits under the plan, less
(B) the value of the assets of the plan.

29 USC 1394 - Application of plan amendments; exception

(a) No plan rule or amendment adopted after January 31, 1981, under section 1389 or 1391 (c) of this title may be applied without the employers consent with respect to liability for a withdrawal or partial withdrawal which occurred before the date on which the rule or amendment was adopted.
(b) All plan rules and amendments authorized under this part shall operate and be applied uniformly with respect to each employer, except that special provisions may be made to take into account the creditworthiness of an employer. The plan sponsor shall give notice to all employers who have an obligation to contribute under the plan and to all employee organizations representing employees covered under the plan of any plan rules or amendments adopted pursuant to this section.

29 USC 1395 - Plan notification to corporation of potentially significant withdrawals

The corporation may, by regulation, require the plan sponsor of a multiemployer plan to provide notice to the corporation when the withdrawal from the plan by any employer has resulted, or will result, in a significant reduction in the amount of aggregate contributions under the plan made by employers.

29 USC 1396 - Special rules for plans under section 404(c) of title 26

(a) Amount of withdrawal liability; determinative factors 
In the case of a plan described in subsection (b) of this section
(1) if an employer withdraws prior to a termination described in section 1341a (a)(2) of this title, the amount of withdrawal liability to be paid in any year by such employer shall be an amount equal to the greater of
(A) the amount determined under section 1399 (c)(1)(C)(i) of this title, or
(B) the product of
(i) the number of contribution base units for which the employer would have been required to make contributions for the prior plan year if the employer had not withdrawn, multiplied by
(ii) the contribution rate for the plan year which would be required to meet the amortization schedules contained in section 1423 (d)(3)(B)(ii) of this title (determined without regard to any limitation on such rate otherwise provided by this subchapter)

except that an employer shall not be required to pay an amount in excess of the withdrawal liability computed with interest; and

(2) the withdrawal liability of an employer who withdraws after December 31, 1983, as a result of a termination described in section 1341a (a)(2) of this title which is agreed to by the labor organization that appoints the employee representative on the joint board of trustees which sponsors the plan, shall be determined under subsection (c) of this section if
(A) as a result of prior employer withdrawals in any plan year commencing after January 1, 1980, the number of contribution base units is reduced to less than 67 percent of the average number of such units for the calendar years 1974 through 1979; and
(B) at least 50 percent of the withdrawal liability attributable to the first 33 percent decline described in subparagraph (A) has been determined by the plan sponsor to be uncollectible within the meaning of regulations of the corporation of general applicability; and
(C) the rate of employer contributions under the plan for each plan year following the first plan year beginning after September 26, 1980 and preceding the termination date equals or exceeds the rate described in section 1423 (d)(3) of this title.
(b) Covered plans 
A plan is described in this subsection if
(1) it is a plan described in section 404 (c) of title 26 or a continuation thereof; and
(2) participation in the plan is substantially limited to individuals who retired prior to January 1, 1976.
(c) Amount of liability of employer; “a year of signatory service” defined 

(1) The amount of an employers liability under this paragraph is the product of
(A) the amount of the employers withdrawal liability determined without regard to this section, and
(B) the greater of 90 percent, or a fraction
(i) the numerator of which is an amount equal to the portion of the plans unfunded vested benefits that is attributable to plan participants who have a total of 10 or more years of signatory service, and
(ii) the denominator of which is an amount equal to the total unfunded vested benefits of the plan.
(2) For purposes of paragraph (1), the term a year of signatory service means a year during any portion of which a participant was employed for an employer who was obligated to contribute in that year, or who was subsequently obligated to contribute.

29 USC 1397 - Application of part in case of certain pre-1980 withdrawals; adjustment of covered plan

(a) For the purpose of determining the amount of unfunded vested benefits allocable to an employer for a partial or complete withdrawal from a plan which occurs after September 25, 1980, and for the purpose of determining whether there has been a partial withdrawal after such date, the amount of contributions, and the number of contribution base units, of such employer properly allocable
(1) to work performed under a collective bargaining agreement for which there was a permanent cessation of the obligation to contribute before September 26, 1980, or
(2) to work performed at a facility at which all covered operations permanently ceased before September 26, 1980, or for which there was a permanent cessation of the obligation to contribute before that date,

shall not be taken into account.

(b) A plan may, in a manner not inconsistent with regulations, which shall be prescribed by the corporation, adjust the amount of unfunded vested benefits allocable to other employers under a plan maintained by an employer described in subsection (a) of this section.

29 USC 1398 - Withdrawal not to occur because of change in business form or suspension of contributions during labor dispute

Notwithstanding any other provision of this part, an employer shall not be considered to have withdrawn from a plan solely because
(1) an employer ceases to exist by reason of
(A) a change in corporate structure described in section 1369 (b) of this title, or
(B) a change to an unincorporated form of business enterprise,

if the change causes no interruption in employer contributions or obligations to contribute under the plan, or

(2) an employer suspends contributions under the plan during a labor dispute involving its employees.

For purposes of this part, a successor or parent corporation or other entity resulting from any such change shall be considered the original employer.

29 USC 1399 - Notice, collection, etc., of withdrawal liability

(a) Furnishing of information by employer to plan sponsor 
An employer shall, within 30 days after a written request from the plan sponsor, furnish such information as the plan sponsor reasonably determines to be necessary to enable the plan sponsor to comply with the requirements of this part.
(b) Notification, demand for payment, and review upon complete or partial withdrawal by employer 

(1) As soon as practicable after an employers complete or partial withdrawal, the plan sponsor shall
(A) notify the employer of
(i) the amount of the liability, and
(ii) the schedule for liability payments, and
(B) demand payment in accordance with the schedule.
(2) 
(A) No later than 90 days after the employer receives the notice described in paragraph (1), the employer
(i) may ask the plan sponsor to review any specific matter relating to the determination of the employers liability and the schedule of payments,
(ii) may identify any inaccuracy in the determination of the amount of the unfunded vested benefits allocable to the employer, and
(iii) may furnish any additional relevant information to the plan sponsor.
(B) After a reasonable review of any matter raised, the plan sponsor shall notify the employer of
(i) the plan sponsors decision,
(ii) the basis for the decision, and
(iii) the reason for any change in the determination of the employers liability or schedule of liability payments.
(c) Payment requirements; amount, etc. 

(1) 
(A) 
(i) Except as provided in subparagraphs (B) and (D) of this paragraph and in paragraphs (4) and (5), an employer shall pay the amount determined under section 1391 of this title, adjusted if appropriate first under section 1389 of this title and then under section 1386 of this title over the period of years necessary to amortize the amount in level annual payments determined under subparagraph (C), calculated as if the first payment were made on the first day of the plan year following the plan year in which the withdrawal occurs and as if each subsequent payment were made on the first day of each subsequent plan year. Actual payment shall commence in accordance with paragraph (2).
(ii) The determination of the amortization period described in clause (i) shall be based on the assumptions used for the most recent actuarial valuation for the plan.
(B) In any case in which the amortization period described in subparagraph (A) exceeds 20 years, the employers liability shall be limited to the first 20 annual payments determined under subparagraph (C).
(C) 
(i) Except as provided in subparagraph (E), the amount of each annual payment shall be the product of
(I) the average annual number of contribution base units for the period of 3 consecutive plan years, during the period of 10 consecutive plan years ending before the plan year in which the withdrawal occurs, in which the number of contribution base units for which the employer had an obligation to contribute under the plan is the highest, and
(II) the highest contribution rate at which the employer had an obligation to contribute under the plan during the 10 plan years ending with the plan year in which the withdrawal occurs.

For purposes of the preceding sentence, a partial withdrawal described in section 1385 (a)(1) of this title shall be deemed to occur on the last day of the first year of the 3-year testing period described in section 1385 (b)(1)(B)(i) of this title.

(ii) 
(I) A plan may be amended to provide that for any plan year ending before 1986 the amount of each annual payment shall be (in lieu of the amount determined under clause (i)) the average of the required employer contributions under the plan for the period of 3 consecutive plan years (during the period of 10 consecutive plan years ending with the plan year preceding the plan year in which the withdrawal occurs) for which such required contributions were the highest.
(II) Subparagraph (B) shall not apply to any plan year to which this clause applies.
(III) This clause shall not apply in the case of any withdrawal described in subparagraph (D).
(IV) If under a plan this clause applies to any plan year but does not apply to the next plan year, this clause shall not apply to any plan year after such next plan year.
(V) For purposes of this clause, the term required contributions means, for any period, the amounts which the employer was obligated to contribute for such period (not taking into account any delinquent contribution for any other period).
(iii) A plan may be amended to provide that for the first plan year ending on or after September 26, 1980, the number 5 shall be substituted for the number 10 each place it appears in clause (i) or clause (ii) (whichever is appropriate). If the plan is so amended, the number 5 shall be increased by one for each succeeding plan year until the number 10 is reached.
(D) In any case in which a multiemployer plan terminates by the withdrawal of every employer from the plan, or in which substantially all the employers withdraw from a plan pursuant to an agreement or arrangement to withdraw from the plan
(i) the liability of each such employer who has withdrawn shall be determined (or redetermined) under this paragraph without regard to subparagraph (B), and
(ii) notwithstanding any other provision of this part, the total unfunded vested benefits of the plan shall be fully allocated among all such employers in a manner not inconsistent with regulations which shall be prescribed by the corporation.

Withdrawal by an employer from a plan, during a period of 3 consecutive plan years within which substantially all the employers who have an obligation to contribute under the plan withdraw, shall be presumed to be a withdrawal pursuant to an agreement or arrangement, unless the employer proves otherwise by a preponderance of the evidence.

(E) In the case of a partial withdrawal described in section 1385 (a) of this title, the amount of each annual payment shall be the product of
(i) the amount determined under subparagraph (C) (determined without regard to this subparagraph), multiplied by
(ii) the fraction determined under section 1386 (a)(2) of this title.
(2) Withdrawal liability shall be payable in accordance with the schedule set forth by the plan sponsor under subsection (b)(1) of this section beginning no later than 60 days after the date of the demand notwithstanding any request for review or appeal of determinations of the amount of such liability or of the schedule.
(3) Each annual payment determined under paragraph (1)(C) shall be payable in 4 equal installments due quarterly, or at other intervals specified by plan rules. If a payment is not made when due, interest on the payment shall accrue from the due date until the date on which the payment is made.
(4) The employer shall be entitled to prepay the outstanding amount of the unpaid annual withdrawal liability payments determined under paragraph (1)(C), plus accrued interest, if any, in whole or in part, without penalty. If the prepayment is made pursuant to a withdrawal which is later determined to be part of a withdrawal described in paragraph (1)(D), the withdrawal liability of the employer shall not be limited to the amount of the prepayment.
(5) In the event of a default, a plan sponsor may require immediate payment of the outstanding amount of an employers withdrawal liability, plus accrued interest on the total outstanding liability from the due date of the first payment which was not timely made. For purposes of this section, the term default means
(A) the failure of an employer to make, when due, any payment under this section, if the failure is not cured within 60 days after the employer receives written notification from the plan sponsor of such failure, and
(B) any other event defined in rules adopted by the plan which indicates a substantial likelihood that an employer will be unable to pay its withdrawal liability.
(6) Except as provided in paragraph (1)(A)(ii), interest under this subsection shall be charged at rates based on prevailing market rates for comparable obligations, in accordance with regulations prescribed by the corporation.
(7) A multiemployer plan may adopt rules for other terms and conditions for the satisfaction of an employers withdrawal liability if such rules
(A) are consistent with this chapter, and
(B) are not inconsistent with regulations of the corporation.
(8) In the case of a terminated multiemployer plan, an employers obligation to make payments under this section ceases at the end of the plan year in which the assets of the plan (exclusive of withdrawal liability claims) are sufficient to meet all obligations of the plan, as determined by the corporation.
(d) Applicability of statutory prohibitions 
The prohibitions provided in section 1106 (a) of this title do not apply to any action required or permitted under this part.

29 USC 1400 - Approval of amendments

(a) Amendment of covered multiemployer plan; procedures applicable 
Except as provided in subsection (b) of this section, if an amendment to a multiemployer plan authorized by any preceding section of this part is adopted more than 36 months after the effective date of this section, the amendment shall be effective only if the corporation approves the amendment, or, within 90 days after the corporation receives notice and a copy of the amendment from the plan sponsor, fails to disapprove the amendment.
(b) Amendment respecting methods for computing withdrawal liability 
An amendment permitted by section 1391 (c)(5) of this title may be adopted only in accordance with that section.
(c) Criteria for disapproval by corporation 
The corporation shall disapprove an amendment referred to in subsection (a) or (b) of this section only if the corporation determines that the amendment creates an unreasonable risk of loss to plan participants and beneficiaries or to the corporation.

29 USC 1401 - Resolution of disputes

(a) Arbitration proceedings; matters subject to arbitration, procedures applicable, etc. 

(1) Any dispute between an employer and the plan sponsor of a multiemployer plan concerning a determination made under sections 1381 through 1399 of this title shall be resolved through arbitration. Either party may initiate the arbitration proceeding within a 60-day period after the earlier of
(A) the date of notification to the employer under section 1399 (b)(2)(B) of this title, or
(B) 120 days after the date of the employers request under section 1399 (b)(2)(A) of this title.

The parties may jointly initiate arbitration within the 180-day period after the date of the plan sponsors demand under section 1399 (b)(1) of this title.

(2) An arbitration proceeding under this section shall be conducted in accordance with fair and equitable procedures to be promulgated by the corporation. The plan sponsor may purchase insurance to cover potential liability of the arbitrator. If the parties have not provided for the costs of the arbitration, including arbitrators fees, by agreement, the arbitrator shall assess such fees. The arbitrator may also award reasonable attorneys fees.
(3) 
(A) For purposes of any proceeding under this section, any determination made by a plan sponsor under sections 1381 through 1399 of this title and section 1405 of this title is presumed correct unless the party contesting the determination shows by a preponderance of the evidence that the determination was unreasonable or clearly erroneous.
(B) In the case of the determination of a plans unfunded vested benefits for a plan year, the determination is presumed correct unless a party contesting the determination shows by a preponderance of evidence that
(i) the actuarial assumptions and methods used in the determination were, in the aggregate, unreasonable (taking into account the experience of the plan and reasonable expectations), or
(ii) the plans actuary made a significant error in applying the actuarial assumptions or methods.
(b) Alternative collection proceedings; civil action subsequent to arbitration award; conduct of arbitration proceedings 

(1) If no arbitration proceeding has been initiated pursuant to subsection (a) of this section, the amounts demanded by the plan sponsor under section 1399 (b)(1) of this title shall be due and owing on the schedule set forth by the plan sponsor. The plan sponsor may bring an action in a State or Federal court of competent jurisdiction for collection.
(2) Upon completion of the arbitration proceedings in favor of one of the parties, any party thereto may bring an action, no later than 30 days after the issuance of an arbitrators award, in an appropriate United States district court in accordance with section 1451 of this title to enforce, vacate, or modify the arbitrators award.
(3) Any arbitration proceedings under this section shall, to the extent consistent with this subchapter, be conducted in the same manner, subject to the same limitations, carried out with the same powers (including subpena power), and enforced in United States courts as an arbitration proceeding carried out under title 9.
(c) Presumption respecting finding of fact by arbitrator 
In any proceeding under subsection (b) of this section, there shall be a presumption, rebuttable only by a clear preponderance of the evidence, that the findings of fact made by the arbitrator were correct.
(d) Payments by employer prior and subsequent to determination by arbitrator; adjustments; failure of employer to make payments 
Payments shall be made by an employer in accordance with the determinations made under this part until the arbitrator issues a final decision with respect to the determination submitted for arbitration, with any necessary adjustments in subsequent payments for overpayments or underpayments arising out of the decision of the arbitrator with respect to the determination. If the employer fails to make timely payment in accordance with such final decision, the employer shall be treated as being delinquent in the making of a contribution required under the plan (within the meaning of section 1145 of this title).
(e) Furnishing of information by plan sponsor to employer respecting computation of withdrawal liability of employer; fees 
If any employer requests in writing that the plan sponsor make available to the employer general information necessary for the employer to compute its withdrawal liability with respect to the plan (other than information which is unique to that employer), the plan sponsor shall furnish the information to the employer without charge. If any employer requests in writing that the plan sponsor make an estimate of such employers potential withdrawal liability with respect to the plan or to provide information unique to that employer, the plan sponsor may require the employer to pay the reasonable cost of making such estimate or providing such information.
(f) Procedures applicable to certain disputes 

(1) In general 
If
(A) a plan sponsor of a plan determines that
(i) a complete or partial withdrawal of an employer has occurred, or
(ii) an employer is liable for withdrawal liability payments with respect to the complete or partial withdrawal of an employer from the plan,
(B) such determination is based in whole or in part on a finding by the plan sponsor under section 1392 (c) of this title that a principal purpose of a transaction that occurred before January 1, 1999, was to evade or avoid withdrawal liability under this subtitle, and
(C) such transaction occurred at least 5 years before the date of the complete or partial withdrawal,

then the special rules under paragraph (2) shall be used in applying subsections (a) and (d) of this section and section 1399 (c) of this title to the employer.

(2) Special rules 

(A) Determination 
Notwithstanding subsection (a)(3) of this section
(i) a determination by the plan sponsor under paragraph (1)(B) shall not be presumed to be correct, and
(ii) the plan sponsor shall have the burden to establish, by a preponderance of the evidence, the elements of the claim under section 1392 (c) of this title that a principal purpose of the transaction was to evade or avoid withdrawal liability under this subtitle.

Nothing in this subparagraph shall affect the burden of establishing any other element of a claim for withdrawal liability under this subtitle.

(B) Procedure 
Notwithstanding subsection (d) of this section and section 1399 (c) of this title, if an employer contests the plan sponsors determination under paragraph (1) through an arbitration proceeding pursuant to subsection (a) of this section, or through a claim brought in a court of competent jurisdiction, the employer shall not be obligated to make any withdrawal liability payments until a final decision in the arbitration proceeding, or in court, upholds the plan sponsors determination.
(g) Procedures applicable to certain disputes 

(1) In general.— 
If
(A) a plan sponsor of a plan determines that
(i) a complete or partial withdrawal of an employer has occurred, or
(ii) an employer is liable for withdrawal liability payments with respect to such complete or partial withdrawal, and
(B) such determination is based in whole or in part on a finding by the plan sponsor under section 1392 (c) of this title that a principal purpose of any transaction which occurred after December 31, 1998, and at least 5 years (2 years in the case of a small employer) before the date of the complete or partial withdrawal was to evade or avoid withdrawal liability under this subtitle,

then the person against which the withdrawal liability is assessed based solely on the application of section 1392 (c) of this title may elect to use the special rule under paragraph (2) in applying subsection (d) of this section and section 1399 (c) of this title to such person.

(2) Special rule.— 
Notwithstanding subsection (d) and section 1399 (c) of this title, if an electing person contests the plan sponsors determination with respect to withdrawal liability payments under paragraph (1) through an arbitration proceeding pursuant to subsection (a), through an action brought in a court of competent jurisdiction for review of such an arbitration decision, or as otherwise permitted by law, the electing person shall not be obligated to make the withdrawal liability payments until a final decision in the arbitration proceeding, or in court, upholds the plan sponsors determination, but only if the electing person
(A) provides notice to the plan sponsor of its election to apply the special rule in this paragraph within 90 days after the plan sponsor notifies the electing person of its liability by reason of the application of section 1392 (c) of this title; and
(B) if a final decision in the arbitration proceeding, or in court, of the withdrawal liability dispute has not been rendered within 12 months from the date of such notice, the electing person provides to the plan, effective as of the first day following the 12-month period, a bond issued by a corporate surety company that is an acceptable surety for purposes of section 1112 of this title, or an amount held in escrow by a bank or similar financial institution satisfactory to the plan, in an amount equal to the sum of the withdrawal liability payments that would otherwise be due under subsection (d) and section 1399 (c) of this title for the 12-month period beginning with the first anniversary of such notice. Such bond or escrow shall remain in effect until there is a final decision in the arbitration proceeding, or in court, of the withdrawal liability dispute, at which time such bond or escrow shall be paid to the plan if such final decision upholds the plan sponsors determination.
(3) Definition of small employer.— 
For purposes of this subsection
(A) In general.— 
The term small employer means any employer which, for the calendar year in which the transaction referred to in paragraph (1)(B) occurred and for each of the 3 preceding years, on average
(i) employs not more than 500 employees, and
(ii) is required to make contributions to the plan for not more than 250 employees.
(B) Controlled group.— 
Any group treated as a single employer under subsection (b)(1) of section 1301 of this title, without regard to any transaction that was a basis for the plans finding under section 1392 of this title, shall be treated as a single employer for purposes of this subparagraph.
(4) Additional security pending resolution of dispute.— 
If a withdrawal liability dispute to which this subsection applies is not concluded by 12 months after the electing person posts the bond or escrow described in paragraph (2), the electing person shall, at the start of each succeeding 12-month period, provide an additional bond or amount held in escrow equal to the sum of the withdrawal liability payments that would otherwise be payable to the plan during that period.
(5) The liability of the party furnishing a bond or escrow under this subsection shall be reduced, upon the payment of the bond or escrow to the plan, by the amount thereof.

29 USC 1402 - Reimbursements for uncollectible withdrawal liability

(a) Required supplemental program to reimburse for payments due from employers uncollectible as a result of employer involvement in bankruptcy case or proceedings; program participation, premiums, etc. 
By May 1, 1982, the corporation shall establish by regulation a supplemental program to reimburse multiemployer plans for withdrawal liability payments which are due from employers and which are determined to be uncollectible for reasons arising out of cases or proceedings involving the employers under title 11, or similar cases or proceedings. Participation in the supplemental program shall be on a voluntary basis, and a plan which elects coverage under the program shall pay premiums to the corporation in accordance with a premium schedule which shall be prescribed from time to time by the corporation. The premium schedule shall contain such rates and bases for the application of such rates as the corporation considers to be appropriate.
(b) Discretionary supplemental program to reimburse for payments due from employers uncollectible for other appropriate reasons 
The corporation may provide under the program for reimbursement of amounts of withdrawal liability determined to be uncollectible for any other reasons the corporation considers appropriate.
(c) Payment of cost of program 
The cost of the program (including such administrative and legal costs as the corporation considers appropriate) may be paid only out of premiums collected under such program.
(d) Terms and conditions, limitations, etc., of supplemental program 
The supplemental program may be offered to eligible plans on such terms and conditions, and with such limitations with respect to the payment of reimbursements (including the exclusion of de minimis amounts of uncollectible employer liability, and the reduction or elimination of reimbursements which cannot be paid from collected premiums) and such restrictions on withdrawal from the program, as the corporation considers necessary and appropriate.
(e) Arrangements by corporation with private insurers for implementation of program; election of coverage by participating plans with private insurers 
The corporation may enter into arrangements with private insurers to carry out in whole or in part the program authorized by this section and may require plans which elect coverage under the program to elect coverage by those private insurers.

29 USC 1403 - Withdrawal liability payment fund

(a) Establishment of or participation in fund by plan sponsors 
The plan sponsors of multiemployer plans may establish or participate in a withdrawal liability payment fund.
(b) Definitions 
For purposes of this section, the term withdrawal liability payment fund, and the term fund, mean a trust which
(1) is established and maintained under section 501 (c)(22) of title 26,
(2) maintains agreements which cover a substantial portion of the participants who are in multiemployer plans which (under the rules of the trust instrument) are eligible to participate in the fund,
(3) is funded by amounts paid by the plans which participate in the fund, and
(4) is administered by a Board of Trustees, and in the administration of the fund there is equal representation of
(A) trustees representing employers who are obligated to contribute to the plans participating in the fund, and
(B) trustees representing employees who are participants in plans which participate in the fund.
(c) Payments to plan; amount, criteria, etc. 

(1) If an employer withdraws from a plan which participates in a withdrawal liability payment fund, then, to the extent provided in the trust, the fund shall pay to that plan
(A) the employers unattributable liability,
(B) the employers withdrawal liability payments which would have been due but for section 1388, 1389, 1399, or 1405 of this title,
(C) the employers withdrawal liability payments to the extent they are uncollectible.
(2) The fund may provide for the payment of the employers attributable liability if the fund
(A) provides for the payment of both the attributable and the unattributable liability of the employer in a single payment, and
(B) is subrogated to all rights of the plan against the employer.
(3) For purposes of this section, the term
(A) attributable liability means the excess, if any, determined under the provisions of a plan not inconsistent with regulations of the corporation, of
(i) the value of vested benefits accrued as a result of service with the employer, over
(ii) the value of plan assets attributed to the employer, and
(B) unattributable liability means the excess of withdrawal liability over attributable liability.

Such terms may be further defined, and the manner in which they shall be applied may be prescribed, by the corporation by regulation.

(4) 
(A) The trust of a fund shall be maintained for the exclusive purpose of paying
(i) any amount described in paragraph (1) and paragraph (2), and
(ii) reasonable and necessary administrative expenses in connection with the establishment and operation of the trust and the processing of claims against the fund.
(B) The amounts paid by a plan to a fund shall be deemed a reasonable expense of administering the plan under sections 1103 (c)(1) and 1104 (a)(1)(A)(ii) of this title, and the payments made by a fund to a participating plan shall be deemed services necessary for the operation of the plan within the meaning of section 1108 (b)(2) of this title or within the meaning of section 4975 (d)(2) of title 26.
(d) Application of payments by plan 

(1) For purposes of this part
(A) only amounts paid by the fund to a plan under subsection (c)(1)(A) of this section shall be credited to withdrawal liability otherwise payable by the employer, unless the plan otherwise provides, and
(B) any amounts paid by the fund under subsection (c) of this section to a plan shall be treated by the plan as a payment of withdrawal liability to such plan.
(2) For purposes of applying provisions relating to the funding standard accounts (and minimum contribution requirements), amounts paid from the plan to the fund shall be applied to reduce the amount treated as contributed to the plan.
(e) Subrogation of fund to rights of plan 
The fund shall be subrogated to the rights of the plan against the employer that has withdrawn from the plan for amounts paid by a fund to a plan under
(1) subsection (c)(1)(A) of this section, to the extent not credited under subsection (d)(1)(A) of this section, and
(2) subsection (c)(1)(C) of this section.
(f) Discharge of rights of fiduciary of fund; standards applicable, etc. 
Notwithstanding any other provision of this chapter, a fiduciary of the fund shall discharge the fiduciarys duties with respect to the fund in accordance with the standards for fiduciaries prescribed by this chapter (to the extent not inconsistent with the purposes of this section), and in accordance with the documents and instruments governing the fund insofar as such documents and instruments are consistent with the provisions of this chapter (to the extent not inconsistent with the purposes of this section). The provisions of the preceding sentence shall supersede any and all State laws relating to fiduciaries insofar as they may now or hereafter relate to a fund to which this section applies.
(g) Prohibition on payments from fund to plan where certain labor negotiations involve employer withdrawn or partially withdrawn from plan and continuity of labor organization representing employees continues 
No payments shall be made from a fund to a plan on the occasion of a withdrawal or partial withdrawal of an employer from such plan if the employees representing the withdrawn contribution base units continue, after such withdrawal, to be represented under section 159 of this title (or other applicable labor laws) in negotiations with such employer by the labor organization which represented such employees immediately preceding such withdrawal.
(h) Purchase of insurance by employer 
Nothing in this section shall be construed to prohibit the purchase of insurance by an employer from any other person, to limit the circumstances under which such insurance would be payable, or to limit in any way the terms and conditions of such insurance.
(i) Promulgation of regulations for establishment and maintenance of fund 
The corporation may provide by regulation rules not inconsistent with this section governing the establishment and maintenance of funds, but only to the extent necessary to carry out the purposes of this part (other than section 1402 of this title).

29 USC 1404 - Alternative method of withdrawal liability payments

A multiemployer plan may adopt rules providing for other terms and conditions for the satisfaction of an employers withdrawal liability if such rules are consistent with this chapter and with such regulations as may be prescribed by the corporation.

29 USC 1405 - Limitation on withdrawal liability

(a) Unfunded vested benefits allocable to employer in bona fide sale of assets of employer in arms-length transaction to unrelated party; maximum amount; determinative factors 

(1) In the case of bona fide sale of all or substantially all of the employers assets in an arms-length transaction to an unrelated party (within the meaning of section 1384 (d) of this title), the unfunded vested benefits allocable to an employer (after the application of all sections of this part having a lower number designation than this section), other than an employer undergoing reorganization under title 11 or similar provisions of State law, shall not exceed the greater of
(A) a portion (determined under paragraph (2)) of the liquidation or dissolution value of the employer (determined after the sale or exchange of such assets), or
(B) in the case of a plan using the attributable method of allocating withdrawal liability, the unfunded vested benefits attributable to employees of the employer.
(2) For purposes of paragraph (1), the portion shall be determined in accordance with the following table:
(b) Unfunded vested benefits allocable to insolvent employer undergoing liquidation or dissolution; maximum amount; determinative factors 
In the case of an insolvent employer undergoing liquidation or dissolution, the unfunded vested benefits allocable to that employer shall not exceed an amount equal to the sum of
(1) 50 percent of the unfunded vested benefits allocable to the employer (determined without regard to this section), and
(2) that portion of 50 percent of the unfunded vested benefits allocable to the employer (as determined under paragraph (1)) which does not exceed the liquidation or dissolution value of the employer determined
(A) as of the commencement of liquidation or dissolution, and
(B) after reducing the liquidation or dissolution value of the employer by the amount determined under paragraph (1).
(c) Property not subject to enforcement of liability; precondition 
To the extent that the withdrawal liability of an employer is attributable to his obligation to contribute to or under a plan as an individual (whether as a sole proprietor or as a member of a partnership), property which may be exempt from the estate under section 522 of title 11 or under similar provisions of law, shall not be subject to enforcement of such liability.
(d) Insolvency of employer; liquidation or dissolution value of employer 
For purposes of this section
(1) an employer is insolvent if the liabilities of the employer, including withdrawal liability under the plan (determined without regard to subsection (b) of this section), exceed the assets of the employer (determined as of the commencement of the liquidation or dissolution), and
(2) the liquidation or dissolution value of the employer shall be determined without regard to such withdrawal liability.
(e) One or more withdrawals of employer attributable to same sale, liquidation, or dissolution 
In the case of one or more withdrawals of an employer attributable to the same sale, liquidation, or dissolution, under regulations prescribed by the corporation
(1) all such withdrawals shall be treated as a single withdrawal for the purpose of applying this section, and
(2) the withdrawal liability of the employer to each plan shall be an amount which bears the same ratio to the present value of the withdrawal liability payments to all plans (after the application of the preceding provisions of this section) as the withdrawal liability of the employer to such plan (determined without regard to this section) bears to the withdrawal liability of the employer to all such plans (determined without regard to this section).