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
Yes, that's correct. See the calendar on page 6 in the 2210 instructions.
But according to this
Example 2.
You had a $500 underpayment remaining after your April 15 payment. The June 15 installment required a payment of $1,200. On June 10, you made a payment of $1,200 to cover the June 15 installment. However, $500 of this payment is applied first to the April 15 installment. The penalty for the April 15 installment is figured from April 15 to June 10 (56 days). The amount remaining to be applied to the June 15 installment is $700.
If I've paid my tax on June 10, the penalty is from April 15 to June 10 and not till end of June. But I've not found anywhere in TurboTax that allow me to enter this information
Still wondering this. I don't think TurboTax is correct
TurboTax indeed calculates on its Underpayment Penalty Worksheet based on the number of days late. Lateness is determined by how many days beyond the due date of the particular payment the payment is made.
The calculation done by TurboTax is only an estimate. The IRS does its own calculation based on the dates that your tax account shows for the dates of payment.