Underpayment Penalty - Date Calculation

[nwm]

When I was figuring my underpayment penalty on TurboTax, I was asked which date I would pay the tax owed. I chose 03/08/21 thinking I would mail a check the next day, but I have decided to wait until my return is processed before paying. Is waiting increasing my penalty, or will my underpayment penalty be accurate as long as I pay before 04/15/21? I can't imagine it would fluctuate by more than a few dollars (my penalty was a small amount), so I am more interested in how this works than anything. When I reviewed my tax return, I could not find a reference to the date (03/08/21) that I had inputted or a number of days until payment or anything of that nature that was part of the underpayment calculation.

[Mike9241]

the penalty is computed through 4/15/21  or the date of payment whichever is first. 

[2018problems]

Why 15 April if the due date is 17 May?

In the step-by-step (Premier download) it will use the earlier if 15 April or your pay date. If I pay 17 May will it calc based on 15 April?

[Critter-3]

The penalty is calculated as of the date you pay or the filing deadline (which is 5/17 for the 2020 returns) whichever happens latter.  

[2018problems]

Agree.   However, April 15 is what it says in the Step-by-step

[Critter-3]

Ignore the old date.