After filing Automatic Extension for 2018, I realized that I had underestimated my taxes and made a special payment to IRS on May 2019. Where do I enter this payment in TurboTax?

When you requested your extension you were supposed to pay your estimated tax due.  Did you enter the payment you made into your tax return?  Go to Federal>Deductions and Credits>Estimates and Other Taxes Paid>Other Income Taxes  This will show up on line 17 of your Form 1040

So to clarify my situation:

1) I filed an extension for my 2018 taxes in April 2019 and paid $XX with my extension filing,

2) In May 2019 I realized that the $XX tax I paid with the extension was not sufficient.

2) So in May 2019, I sent in an additional payment of $YY to IRS.

Where do I include the $YY payment in my Turbotax filing?

Thanks

Rajat

How did you sent it?  Did you use a form?  Which form, 1040ES, 1040V, etc.  Or did you pay directly online and pick the right year 2018?

I did a direct online pay and specified 2018 as the tax year.

Thanks

Rajat