How do I enter a single tax prepayment made in December 2020?

To enter, edit or delete estimated taxes paid (Federal, State, Local) -

• Click on Federal Taxes (Personal using Home and Business)
• Click on Deductions and Credits
• Click on I'll choose what I work on (if shown)
• Scroll down to Estimates and Other Taxes Paid
• On Estimates, click on the start or update button

Or enter estimates paid in the Search box located in the upper right of the online program screen. Click on Jump to estimates paid

Or click on Tax Tools on the left side of the online program screen.
Click on Tools
Click on Topic Search
Type in estimated tax payments, click on GO

Federal estimated taxes paid are entered on Form 1040 Line 26