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M-MTax
Level 15
October 9, 2026

Do not enter the check details on Form 4868. Instead, tell TurboTax you already paid it as a past tax payment:

  1. Open your tax return and go to the Federal tab on the left menu.
  2. Click on Deductions & Credits.
  3. Scroll down until you see the section titled Estimates and Other Taxes Paid and expand it.
  4. Click Start or Revisit next to Estimated Tax Payments.
  5. Look for Federal estimated taxes (Form 1040-ES) or Payments with Extension.
  6. Choose the option indicating you made a payment with an extension request and enter the exact dollar amount of the check you mailed.