I wondered if the problems with line 14 in 2021 Form 2210AI were only occurring this year or had been in TT in previous years. I had a similar large LT CG in March 2018 which had been entered as CG in the first period of 2018 Form 2210 and used my 2018 version of TT to check whether entering my total CG/QD in the QD line and zero in the CG line for the first period changed 14 (a) from the normal method where LT gain was entered as CG input and actual QD was entered as QD input. Both results using 2018 TT were the same showing that TT in the past was correctly scaling both CG and QD in calculating Form 2210AI line 14 as it should be per IRS Pub 505. The incorrect calculation in 2021 TT Form 2210AI appears to be a new issue rather than a long term one so their programmers should know how to do it correctly in 2021 if they just match the programming from those earlier years. We shouldn't have to result to tweaking the input data in 2021 just to get 2021 TT to correctly calculate underpayment penalty.
