http://www.law.cornell.edu/uscode/text/26/402U.S. Code § 402 - Taxability of beneficiary of employees’ trust
(a) Taxability of beneficiary of exempt trust
Except as otherwise provided in this section, any amount actually distributed to any distributee by any employees’ trust described in section 401 (a) which is exempt from tax under section 501 (a) shall be taxable to the distributee, in the taxable year of the distributee in which distributed, under section 72 (relating to annuities).
(b) Taxability of beneficiary of nonexempt trust
(1) Contributions
Contributions to an employees’ trust made by an employer during a taxable year of the employer which ends with or within a taxable year of the trust for which the trust is not exempt from tax under section 501 (a) shall be included in the gross income of the employee in accordance with section 83 (relating to property transferred in connection with performance of services), except that the value of the employee’s interest in the trust shall be substituted for the fair market value of the property for purposes of applying such section.
(2) Distributions
The amount actually distributed or made available to any distributee by any trust described in paragraph (1) shall be taxable to the distributee, in the taxable year in which so distributed or made available, under section 72 (relating to annuities), except that distributions of income of such trust before the annuity starting date (as defined in section 72 (c)(4)) shall be included in the gross income of the employee without regard to section 72 (e)(5) (relating to amounts not received as annuities).
(3) Grantor trusts
A beneficiary of any trust described in paragraph (1) shall not be considered the owner of any portion of such trust under subpart E of part I of subchapter J (relating to grantors and others treated as substantial owners).
(4) Failure to meet requirements of section 410(b)
(A) Highly compensated employees
If 1 of the reasons a trust is not exempt from tax under section 501 (a) is the failure of the plan of which it is a part to meet the requirements of section 401 (a)(26) or 410 (b), then a highly compensated employee shall, in lieu of the amount determined under paragraph (1) or (2) include in gross income for the taxable year with or within which the taxable year of the trust ends an amount equal to the
vested accrued benefit of such employee (other than the employee’s investment in the contract) as of the close of such taxable year of the trust.
(B) Failure to meet coverage tests
If a trust is not exempt from tax under section 501 (a) for any taxable year solely because such trust is part of a plan which fails to meet the requirements of section 401 (a)(26) or 410 (b), paragraphs (1) and (2) shall not apply by reason of such failure to any employee who was not a highly compensated employee during—
(i) such taxable year, or
(ii) any preceding period for which service was creditable to such employee under the plan.
(C) Highly compensated employee
For purposes of this paragraph, the term “highly compensated employee” has the meaning given such term by section 414 (q).