After you file

To clarify, did you withdraw the excess in March 2020 or March 2021? If you withdrew it in 2020 you would have Form 1099-R for the withdrawal already and you will just enter the 1099-R on your 2020 return. And you are talking about an excess contribution to 401k (work retirement account) not a traditional IRA or Roth IRA, correct?

You can check line 1 wages if you had the excess deferral already included. Otherwise you will you will to amend your return to include the excess. Please see FAQ How to amend a tax return for instructions.

To report the excess 401(k) contributions and subsequent distributions, a 2020 plan excess distributed in 2021 please follow the steps below:

1. Login to your TurboTax Account 
2. Click "Federal" from the left side of your screen
3. Scroll  down to "Less Common Income" and click "Show More"
4. Scroll down to "Miscellaneous Income, 1099-A, 1099-C" and click "Start"
5. Select "Other income not already reported on a Form W-2 or Form 1099" and click "Start"
6. On the "Did you receive any other wages?" screen answer "Yes" and click "Continue"
7. Continue until you get to the "Any other earned income" screen, answer "Yes" and click "Continue"
8. On the "Enter Source of Other Earned income" screen select "Other" and click "Continue"
9. On the "Any Other Earned Income" screen enter "2020 Excess 401(k) Deferrals" for the description, enter the amount and click "Done".

Please note for the Tax Year 2021 tax filing due April 15, 2022: 

2021 Forms 1099-R will be issued reporting the excess.

• Form 1099-R with code P in box 7 can be ignored if you reported the excess as described above in 2020. 
• However, the earnings on Form 1099-R with Code 8 in box 7 should be reported in 2021.

If the distribution was for a 2020 excess deferral to a designated Roth account don’t add this amount to your wages on your 2020 return.

Please, see Pub 525 page 11 for additional information.