IRS letter on owing taxes

[gaddman2151]

IRS sent me a letter saying I under paid taxes for 2020.  The income nmbers are correct , but I can't figure where the tax credit amount came from for the estimated taxes paid in 2020

[Critter-3]

That line would consist of estimated tax payments and any 2019 refund that was applied to the 2020 return. Did you apply any of the 2019 Refund to the 2020 return? Review what you entered in the program to see if maybe you made an entry error  in one of those two sections.

[Mike9241]

if you had an overpayment from 2019 that you applied to 2020, Turbotax would have entered that on the tax payments worksheet.  perhaps what you did was entered the overpayment a second time as an estimated tax payment.