To be clear, I was talking about Line 11 on Form 2210. Columns a) - d) are headed by the Payment Due Dates of 4/15, 6/15, 9/15 and 1/15. They should individually represent what you paid on or before each due date, not including any of the previous columns. The sum of these columns should equal Line 33 on Form 1040. There's no overlapping time period for annualization going on as in Schedule AI, which determines the required installments for 4/15, 6/15, 9/15 and 1/15, which appear on Line 10 of Form 2210. It's the comparison of Line 10 with Line 11 for columns a) - d) on Form 2210 which determines underpayment. I found last year's Line 11 done correctly, i.e., columns a) - d) added up to my total payments, there is no column on Line 11 that shows your total payments.
The withholding that comes from my W-2 does not specify the date it was withheld (which was even throughout the year in this case). But I think I did what you are suggesting five years ago on a Form 2210 (checking Box D) because it did reflect a real situation at the time. Spouse worked 1st three months of the year and not the rest. It must have been a drop down box that let me specify the dates for the withholding and the amounts. I suppose TT is not allowing an override of Line 11 col a) to include the 2020 overpayment? It seems that would be preferred, since that would directly address the problem. I haven't tried it, since as is, TT is failing to calculate the penalty even though (without the 2020 credit) it finds an underpayment in tax payments.
