The countdown to the tax-filing deadline is underway.

Most taxpayers have until April 15 to file their federal returns. Residents in Maine and Massachusetts have until April 17 due to local holidays. If you don’t file on time, you risk getting slapped with a late-filing and/or late-payment penalty.

But if you’re missing key documents, dealing with an unexpected life event or simply running out of time to get your taxes done by the deadline, you can file for a six-month extension.

Whatever your reason, It’s a simple process to get those extra months. Here is what you need to do to give yourself the extra time you need.

File for an extension

You can e-file an extension for free using any of the Free File software offered by the major tax preparation companies. These often help you estimate your tax due so you can make a payment. You can also print out Form 4868 and send it in to the IRS address for your state by April 15.

Once the IRS approves your extension, you have until Oct. 15 to file your return.

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What about your tax refund?

If you expect a refund, you won't get it until after you file your tax returns and the IRS processes that return.

Paying the IRS

You still need to pay what you owe by April 15, even if you file for an extension. If you underestimate what you owe, you may end up paying interest on what you don’t pay by the deadline. If you pay less than 90 percent of the tax you owe, you’ll be charged a penalty of 0.5 percent of the underpayment every month until you pay the balance.

State extension

Each state has their own tax-filing extension rules. Check your state's tax authority website for more information.

If you’re abroad

You automatically get two extra months until June 15 to file your federal tax returns without submitting an IRS extension request for if you’re a U.S. citizen or resident alien and you live and work outside the U.S. and Puerto Rico.This also applies to military members serving outside the U.S. and Puerto Rico.

When you do file your return, include a statement that explains why you qualified for the later deadline.

If you can't file by the automatic two-month extension date, you can file a Form 4868 to request an additional extension to Oct. 15. You have until June 15 to file this form.

This article originally appeared on USA TODAY: How to file an extension on taxes