26 USC 6113 - Disclosure of nondeductibility of contributions

(a) General rule 
Each fundraising" target="_blank" title="fundraising">fundraising solicitation by (or on behalf of) an organization to which this section applies shall contain an express statement (in a conspicuous and easily recognizable format) that contributions or gifts to such organization are not deductible as charitable contributions for Federal income tax purposes.
(b) Organizations to which section applies 

(1) In general 
Except as otherwise provided in this subsection, this section shall apply to any organization which is not described in section 170 (c) and which
(A) is described in subsection (c) (other than paragraph (1) thereof) or (d) of section 501 and exempt from taxation under section 501 (a),
(B) is a political organization (as defined in section 527 (e)), or
(C) was an organization described in subparagraph (A) or (B) at any time during the 5-year period ending on the date of the fundraising" target="_blank" title="fundraising">fundraising solicitation or is a successor to an organization so described at any time during such 5-year period.
(2) Exception for small organizations 

(A) Annual gross receipts do not exceed $100,000 
This section shall not apply to any organization the gross receipts of which in each taxable year are normally not more than $100,000.
(B) Multiple organization rule 
The Secretary may treat any group of 2 or more organizations as 1 organization for purposes of subparagraph (A) where necessary or appropriate to prevent the avoidance of this section through the use of multiple organizations.
(3) Special rule for certain fraternal organizations 
For purposes of paragraph (1), an organization described in section 170 (c)(4) shall be treated as described in section 170 (c) only with respect to solicitations for contributions or gifts which are to be used exclusively for purposes referred to in section 170 (c)(4).
(c) Fundraising solicitation 
For purposes of this section
(1) In general 
Except as provided in paragraph (2), the term fundraising" target="_blank" title="fundraising">fundraising solicitation means any solicitation of contributions or gifts which is made
(A) in written or printed form,
(B) by television or radio, or
(C) by telephone.
(2) Exception for certain letters or calls 
The term fundraising" target="_blank" title="fundraising">fundraising solicitation shall not include any letter or telephone call if such letter or call is not part of a coordinated fundraising" target="_blank" title="fundraising">fundraising campaign soliciting more than 10 persons during the calendar year.