If you are self-employed and report on Schedule C, your extension is the same Form 4868 everyone else files. What is different is the size of the April payment, because nobody withheld anything for you all year.
What is due April 15
- Your 2026 income tax and self-employment tax, minus any estimated payments you made.
- Your first 2027 estimated payment, if you owe them.
- The extension request itself.
Self-employment tax is 15.3 percent on net earnings up to the Social Security wage base and 2.9 percent above it. People who extend without paying it are the ones surprised by the November bill.
What the extension does move
Employer contributions to a SEP IRA or a solo 401(k) for 2026 can be made until the extended due date, October 15, 2027, if you extended. That is a real benefit: you can compute the exact allowable contribution from the finished return and fund it in September. The employee deferral portion of a solo 401(k) has earlier deadlines, and traditional or Roth IRA contributions do not move.
Estimating the balance
Take last year's Schedule C and the self-employment tax on it. Adjust for the change in revenue. Subtract the estimated payments you made. Pay the rest with the extension.
Common mistake
Extending because the books are not done, then leaving the books undone until October 14. An extension buys time to do it right, not time to not do it.
Ready to file it?
You can file a personal extension (Form 4868) online in a few minutes with TaxExtension.com, an IRS-authorized e-file provider operated by our publisher. The extension is automatic; the payment is still due on the original date.
Sources
- IRS, About Form 4868
- IRS, Self-employment tax
- IRS, SEP plan FAQs