@Xuser
My point in scaling the numbers backwards in my earlier test cases was to show that TT was not correctly calculating line 14 in order to rebut your comments that TT was working correctly, because it isn't. Additional examples have been provided to show the impact of TT errors that don't involve backward scaling to help others understand the impact of TT error, which isn't trivial if significant CG occurs in these earlier periods.
Also, I checked my old tax files for similar line 14 errors to determine if TT was doing things correctly in the past. I had a similar large LT CG in March 2018 which had been entered as CG in the first period and used 2018 TT to see whether entering my total CG/QD in the QD line and zero in the CG line for the first period changed 14 (a). It did not, thus showing that TT in the past was correctly scaling both CG and QD in calculating Form 2210AI back then per IRS Pub 505. The incorrect calculation in 2021 TT Form 2210AI appears to be a new issue rather than a long term one.
