Can I just report them both for this tax year. How do I amend for 2020? If I don't amend 2020, do I get in troubled?
Yes, generally, you will have to amend your 2020 tax return for a 2021 Form 1099-R code P. If you had taxes withheld then you will have to enter it on your 2021 tax return as well since the withholding is reported in the year that the tax was withheld. The 2022 code P will not do anything to the 2022 tax return but the withholdings will be applied to 2022.
To verify, is there any other code in box 7? Was this an excess from an IRA or 401k?
If it was from a 401k and you had added the excess deferral already to our wages on your 2020 return with the steps below, then you do not need to add the Form 1099-R with code P to your 2020 tax return. Therefore, you don't need to amend your 2020 return.