Form 4868 Extension Planner

No. Form 4868 extends your filing deadline by six months to October 15, but it does not extend the payment deadline. Any tax owed is still due by April 15. If you pay after April 15, the IRS charges failure-to-pay penalty (0.5% per month, up to 25%) plus interest (currently 7% annually) on the unpaid balance.

If you file Form 4868 timely, pay at least 90% of your total tax liability by April 15, and pay the remaining balance when you file (by October 15), the IRS waives the failure-to-pay penalty. Interest still accrues on the unpaid 10%, but the 0.5%/month penalty does not apply.

Without a timely extension, the failure-to-file penalty is 5% per month (up to 25%) of unpaid tax, in addition to the 0.5%/month failure-to-pay penalty. When both apply in the same month, the FTF is reduced by the FTP so the combined rate is 5%/month, not 5.5%. If you file more than 60 days late, the minimum FTF penalty is $525 (for tax year 2025 returns, due April 2026) or 100% of the tax owed, whichever is less — $510 applied to tax year 2024 returns.

The IRS underpayment interest rate is the federal short-term rate plus 3 percentage points, set quarterly by Revenue Ruling. For Q3 2026 the rate is 7% annually, compounded daily. The rate held at 8% throughout 2024 and Q1 2025, dropped to 7% from Q2 2025 through Q1 2026, then briefly to 6% for Q2 2026 before returning to 7% for Q3 2026 onward. Interest on unpaid tax runs from April 15 regardless of whether you filed Form 4868.

No. Form 4868 must be filed by the original April 15 deadline. If April 15 has passed and you haven't filed either the extension or your return, the failure-to-file penalty is already accruing. File as soon as possible — every month (or part of a month) late adds 5% of the unpaid balance until the 25% cap.

Technically yes, but there is no penalty for filing late when no tax is owed. The failure-to-file and failure-to-pay penalties are both calculated as percentages of unpaid tax — if your withholding and payments already cover your liability, both penalties are zero. You have three years from the original due date to file and still receive your refund.

Yes. You can pay through IRS Direct Pay, EFTPS, a debit or credit card, or IRS Online Account and indicate the payment is for Form 4868 — in most cases the payment itself serves as the extension request and you don't need to separately file the paper form. Keep the payment confirmation as proof.

Yes, they're independent obligations. Form 4868 only extends the filing deadline for last year's return; if you also have current-year income that requires quarterly estimated payments (self-employment, investment, rental, etc.), the Q3 installment is still due September 15 regardless of the pending extension. Missing it risks a separate Form 2210 underpayment penalty unless you meet the 90%/100%/110% safe harbor.