If you have an overpayment, it should be reflected on your records with the IRS.
To apply this payment to the current year's taxes in TurboTax:
- Go to Federal > Deductions & Credits
- Scroll down to Estimates and Other Taxes Paid and click Start/Revisit next to Estimated Tax Payments
- Select Start next to Federal estimated taxes for 2021 (Form 1040-ES)
- Yes
- Enter the date of your second payment and amount under Additional payments
