@richardjwaksman I am not an expert but may have some ideas for you to explore.
if you used TurboTax last year and this year, it should have automatically carried forward information from last year that it uses for comparisons. The AGI from last year should have carried forward with it, and would be a “snapshot” of what you filed, which is what the IRS says it has too.
humor me here...try logging on to last year’s TurboTax software and observe if (1) it performs any updates & restarts, and (2) if your refund amount/tax owed amount changes from when you actually filed.
if the amount changes, chances are your AGI was affected as well. You may want to compare numbers from your “new” 2020 1040 form to a copy of what you filed, so you can see what may have changed.
(I had a similar issue with this year’s return - as it turns out there was legislation passed in mid-March that affected the rules. I only learned this because I had already e-filed Federal but had waited to file my state by mail. In the amount of time since I filed Federal and then logged on again to print my state filing copy, all my numbers changed as a result.)
