When you process an underpayment penalty, you specify the date you will pay. If you select a different date when you file, Turbo Tax doesn't appear to adjust your tax.

[kcmidi]

In my case it was over $100 different when I went back to the original form. Just an FYI since I don't see any way to tell Turbo directly.

[VolvoGirl · Accepted solution]

When you pay the 2023 tax due doesn't affect the underpayment penalty on line 38.

It's not for filing or paying late.  It doesn't have to do with last year's tax return or not paying estimates for this year.  The penalty is an "estimated" amount.    It's a penalty if you owe too much or for not paying in enough withholding during the year or not paying in evenly.  

You might be able to eliminate it or at least reduce it.  You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you.  It's form 2210.

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

Underpayment Penalties - Click the Start or update button