Since latest update of TT on 3/11/22 still doesn't fix any of the issues with Forms 2210 and 2210AI, TT may never fix the remaining problems including the issue with line 11 not crediting prior year refund as a tax payment. In lieu of including 2020 refund as a tax payment credited to 2021 tax return, just include the amount of 2020 refund as a fifth estimated tax payment with the paid date being the date that your 2020 return was filed and/or accepted by IRS. Looking at the tax payment worksheet in TT, this would result in the same total of estimated tax payments and refund credits for the year and should result in TT increasing line 11 by the amount of the 2020 refund (via the fifth estimated payment tweak) in the appropriate period when the 2020 return was filed which should eliminate the bogus underpayment penalty due to TT error on this line.
