Amend 8606?

Clients’ 2020 return has been filed. In 2020, spouse converted 2019 traditional IRA contribution to Roth. So Form 8606 was filed with 2020 return. Client now tells me spouse made a 2020 traditional IRA contribution in 2021 and he’s about to convert that to her Roth. Can/ should I amend just the 2020 8606 to show the additional basis for the 2020 contribution? I’ve been told that amending the whole 1040 with no change in the ultimate tax will cause problems and only confuse the IRS.

An 8606 can be filed as a standalone document. Write "Amended" across the top.

Thank you. I assume there wouldn’t be a penalty for this? No failure to file since we did file the form 8606 with the original return and no $100 penalty for overstated basis since we understated our basis. Is there an understated basis penalty? I don’t see one.

I've filed a few, never a penalty.