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You mail IRS Form 4868 to the service center for your state before the filing deadline; the exact address depends on your state and whether you're enclosing a payment. The extension gives you more time to file, not more time to pay: interest still runs on any balance owed. File electronically if you can; paper is the backup.
This is general information, not tax advice.
| Step | Details |
|---|---|
| Get Form 4868 | The one-page "Application for Automatic Extension of Time to File." Available on irs.gov. |
| Fill it out | Your name, address, SSN, an estimate of your total tax liability, and what you've already paid. |
| Find the right address | The IRS assigns service centers by state, and the address differs depending on whether you're enclosing a payment. Check the form's instructions for your line. |
| Mail it before the deadline | The envelope must be postmarked by the filing deadline. Near the deadline, send it certified. |
| Pay what you owe anyway | The extension covers filing, not payment. Send your best estimate of the balance with the form or pay online. |
An automatic six-month extension to file your return: no reason required, no approval needed. File the form and you get the time. What it does not give you is extra time to pay. Interest starts running on any unpaid balance from the original deadline, and the late-payment penalty accrues too, just at a lower rate than the failure-to-file penalty. This is the single most misunderstood point in tax extensions: the extension protects you from the harsh penalty for filing late, but the meter is still running on what you owe.
The practical move is to estimate your tax as accurately as you can and pay that estimate with the extension. If you overpay, the excess comes back as a refund. If you underpay, you owe interest on the difference, but you've avoided the big penalty. A rough payment beats no payment every time.
Most people should e-file the extension: it's faster, you get confirmation, and there's no envelope to lose. Paper filing makes sense in specific situations: you can't e-file for some reason, you prefer a paper trail you control, or you're already mailing a payment and want everything in one envelope. If you do mail it, the postmark is what counts: a form postmarked by the deadline is on time even if it arrives days later. That's the "timely mailed is timely filed" rule, and it's why certified mail near the deadline is worth it. The green card or the electronic confirmation is your proof if the IRS ever says the form arrived late.
One caution: the form has to be complete and legible. An extension form with a missing SSN or an unreadable address can be rejected, and a rejected extension is the same as no extension. Double-check the basics before it goes in the envelope.
Federal and state extensions are separate. Some states grant an automatic extension when you file the federal one; others want their own form; a few don't have an extension process at all and just charge you for filing late. Check your state's revenue department before assuming the federal form covers you. The same file-versus-pay distinction usually applies at the state level too.
Canada doesn't have an equivalent of Form 4868. The CRA expects your return by the deadline (April 30 for most individuals, June 15 if you're self-employed, though any balance owed is still due April 30), and filing late triggers a late-filing penalty plus interest. There is no form that buys you six months. If you can't file on time, file as soon as you can and pay what you owe: the penalties grow with delay, so every week matters.
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