From Notice 1989-32 (Note that Form W-2P was the form used to report these distributions before Form 1099-R became the form to be used, but the rules are the same):
Corrective Distributions of Excess Deferrals
If a corrective distribution of excess deferrals and income is made timely in the year after the year of the deferral, and the TAMRA rule is used to treat the income on the excess deferral as income for the year of distribution, two separate Forms W-2P must be filed for the year of distribution. The portion of the distribution representing the excess deferral (unadjusted for income) is reported in both the gross distribution box and the taxable amount box on one Form W-2P, and the appropriate distribution code (code "P" for the taxable year before the distribution year) is specified in the code box. The portion of the distribution representing the income on the excess deferral is reported in both the gross distribution box and the taxable amount box on a second Form W-2P, and a current year distribution code (code "8") is specified in the code box. If income on the excess deferral is negative (due to net losses), the reporting procedures described below under " Loss on Excess Deferral " should be followed.
