How to amend prior year return for excess 401K contribution?

[vadimrapp]

In 2023 the audit of my employer's 401K plan failed nondiscrimination test, and about $4.6K was returned to me as a distribution; consequently, in 2024 I received form 1099-R for that distribution. When I entered it in TurboTax for 2023, TT showed the following message:

• It looks like you may need to amend your 2022 return. Here's why: Your 1099-R reports earnings on a contribution you made in 2022. This information needs to go on your 2022 return.

I'm not sure why it mentions earnings - the field #3, "capital gain" is empty, and determining what if anything was gained on that excess contribution probably would be nontrivial task. But more important, what specifically should I amend in 2022 return?

[DanaB27]

Your 2023 Form 1099-R with code P will have to be entered on your 2022 amended return as shown on the Form. Since the excess deferral was made for 2022 this belongs on your 2022 tax return. TurboTax will walk you through the process.

Please see How do I amend my federal tax return for a prior year?

Please see Pub 525 for additional information.