I am also being impacted by the errors/issues on Form 2210/2210AI being reported by @EdRaleigh and @babyrd55 here:
2021 Form 2210 Calculation Error
Form 2210 TY 2021 error
I have an additional issue. The Form 2210 Worksheet allows no edits. In the 4th quarter section (d), it calculates the 4th quarter interest/underpayment penalty through April 15th with no ability to change that date. The IRS only requires interest to be paid through the payment date, which for me will happen well before April 15th. Thus Turbo Tax is calculating too much interest/payment.
I also tried to override the total penalty amount on Form 2210 itself (line 19), but that number is also not editable.
How am I supposed to get this right and not overpay?
Kipa
