If you don’t think you’ll be able to file your taxes by May 17, there’s no reason to panic. Getting a filing extension is a fairly painless process, but there are a few things you should know before you do so.

The easiest way is via Free File. The service can be requested electronically and will automatically extend your filing date until Oct. 15.

You will, though, need to estimate your tax liability, even if you haven’t calculated it. And if that estimate means you’ll owe taxes, you’ll have to pay that estimate by the May 17 deadline. So while you can avoid the paperwork and exact calculations, you can’t put off payments if you know you’re going to owe money.

An alternative to that is getting an automatic six-month extension by using IRS Form 4868. This form, too, will require you to estimate your tax liability, based on the data available to you, but you won’t have to make a payment immediately. Be aware, though, that you will owe interest on your tax bill if you end up owing money.

If you’re planning to file for an extension, it’s not a good idea to wait until the last minute. Three years ago, the online service went offline owing, in part, to a flood of people who had stalled on filing for an exemption, causing all sorts of headaches.

And in a year where the IRS is already overwhelmed and struggling to get refunds out to people, it’s in your best interest not to add to the confusion.

More must-read finance coverage from Fortune:

• Everything to know about Biden’s $3,000 child tax credit—including when the money should arrive
• Should you “sell in May”? Not this year, say experts
• 3 reasons Verizon needed to dump what’s left of AOL and Yahoo
• Are CFOs flocking to Bitcoin? No way, says this high-level adviser
• Commentary: 5 things Western investors misunderstand about China