The underpayment penalty worksheet seems to be incorrect. It always count using the last day of the quarter to calculate the days late and thus the penalty, but it's possible that before that day, the tax has already been payed fully.
Say that by 06/15/2023, $3000 tax is not payed yet. Those are payed by 07/15/2023 with normal tax withholding. However, the underpayment penalty worksheet turbotax generate count that tax to be payed only at the end of the quarter, 09/15/2023, causing a 60 more day late in counting the penalty
