26 USC 269A - Personal service corporations formed or availed of to avoid or evade income tax

(a) General rule 
(1) substantially all of the services of a personal service corporation are performed for (or on behalf of) 1 other corporation, partnership, or other entity, and
(2) the principal purpose for forming, or availing of, such personal service corporation is the avoidance or evasion of Federal income tax by reducing the income of, or securing the benefit of any expense, deduction, credit, exclusion, or other allowance for, any employee-owner which would not otherwise be available,

then the Secretary may allocate all income, deductions, credits, exclusions, and other allowances between such personal service corporation and its employee-owners, if such allocation is necessary to prevent avoidance or evasion of Federal income tax or clearly to reflect the income of the personal service corporation or any of its employee-owners.

(b) Definitions 
For purposes of this section
(1) Personal service corporation 
The term personal service corporation means a corporation the principal activity of which is the performance of personal services and such services are substantially performed by employee-owners.
(2) Employee-owner 
The term employee-owner means any employee who owns, on any day during the taxable year, more than 10 percent of the outstanding stock of the personal service corporation. For purposes of the preceding sentence, section 318 shall apply, except that 5 percent shall be substituted for 50 percent in section 318 (a)(2)(C).
(3) Related persons 
All related persons (within the meaning of section 144 (a)(3)) shall be treated as 1 entity.