Quick answer: if you owe U.S. federal income tax, the amount is generally due by the tax filing deadline—April 15, 2026 for 2025 returns —even if you file for an extension.

What that means

  • Pay by April 15 to avoid extra interest and penalties on unpaid tax.
  • If you can’t pay in full , the IRS may give you more time through a payment plan; one source notes the IRS can generally collect assessed tax for 10 years from the assessment date.
  • For many taxpayers, the filing deadline and payment deadline are the same.

If you already missed it

  • The balance starts accruing interest and penalties once it’s unpaid after the due date.
  • If you received an IRS notice like a CP14 , one source says it typically gives 30 days before enforcement actions can begin.

Simple rule of thumb

  • Owe taxes? Pay by the filing deadline.
  • Need more time? File on time, then arrange payment quickly.
  • Can’t pay at all? Set up a payment plan rather than ignoring it.

If you want, I can also tell you the exact deadline for your state or explain the best IRS payment option for your situation.