@sandy4042 You say " the program is not crediting my overpayment at all, on any column of line 11, it's not divvying it up into equal amounts". The fourth column should match what you put in for the whole year and the numbers on the 1040 proper. Is you overpayment accounted for in the first part of the TT data? Most people have commented that the fourth column has the same calculation results as the full year calculation outside the 2210.
I think the point of checking Box D was to allow entering the withholding in the quarter that you received it and maybe reduce any first quarter penalty caused by the TT leaving out the overpayment. For the purposes of this 2210 error discussion you could adjust the withholding to correct for the lost 2020 overpayment. In other words, increase the withholding by the amount of overpayment not credited in the first quarter in column 1 of 2210. I think this is a work around to the lost underpayment and it only works to the extent you have withholding greater than the overpayment.
As with any of these workarounds, keep good notes and possibly a correct 2210 calculation outside of TT for audit purposes.
