Thanks for your reply, @wmpyoungx. I think my overpayment from 2020 is in all the correct fields with the one exception of Form 2210, line 11, col a). It carried over from my 2020 return prepared by TT, which knows that I applied it to 2021. I also filed by April 15th, didn't use the one-time extended date of May 17th. This correct amount does show on my Tax Payments Worksheet on line 6. It is also included in Line 26 of the 1040 ("2021 estimated tax payments and amount applied from 2020 return"). I did check Box C on Form 2210 for "use annualized income installment method" which triggered Schedule AI to be filled out. I did not check Box D, "figure federal withholding as paid on the dates withheld, instead of equal amounts on the payment due dates". What I see in line 11 col a) - d) are my estimated tax payments for each of the four payment dates plus, for each, my withholding divided by 4. But no 2020 overpayment applied in any of the columns.
Then in Part III Penalty Computation of Schedule 2210, an underpayment is calculated for the first two payment dates due to the 2020 overpayment not being applied. But curiously, Line 19 Penalty, shows zero. So I don't have to do any overrides but am cautiously waiting to see if when I file, the IRS will reject the return, auto flagging as it were for no penalty shown.
