How to file a tax extension, if you think you’ll miss today’s IRS tax-filing deadline

Even though the filing deadline is one of the most well-known (and dreaded) dates on calendar, tax day can still sneak up on people.

Don’t panic. The Internal Revenue Service will grant you an extension without any real fuss. The hiccup there, though: you’ll still have to mail them a check today for any taxes you expect to owe.

It’s confusing, we know. Let’s see if we can make some sense of it all for you.

How do I file a tax extension?

Head over to the IRS Free File site. From there, you can electronically request an extension that automatically extends your filing date until Oct. 16.

If you’re using tax software from TurboTax, e-File or H&R Block, you can also use those to make the request. Or, if you’re especially old school, you can file via mail using Form 4868 or via your tax professional.

I have to pay my taxes now? What’s that about?

While the IRS will give you some extra time to get your paperwork done, it’s less patient with the money you owe. You’ll need to estimate your tax liability, even if you haven’t calculated it and pay whatever you think you’ll owe by today’s deadline.

There is one way to avoid sending money in immediately. If you opt to user IRS Form 4868, you’ll also get an automatic six-month extension. This form, too, will require you to estimate your tax liability, but you won't have to make a payment immediately. Here’s the hiccup: You’ll have to pay interest on your tax bill if you end up owing money.

What happens if I pay my taxes late?

Bottom line? You’ll owe more.

There are two kinds of fees and penalties the IRS tacks on for late payers — one for filing late and another for paying late. If you file your return more than 60 days late, you’re likely looking at a minimum penalty of $210 (unless you owe less than that — in which case the penalty is 100% of the unpaid tax). Otherwise, the fee can be as much as 5% of the unpaid tax each month up to a maximum of 25%.

Late payment penalties are generally 0.5% of the unpaid tax per month, though that can build to as much as 25%. If things get that bad, the IRS is usually willing to take a lower amount via a payment agreement.

I’m usually on time with my payments, but can’t afford what I owe right now. How much trouble am I in?

You might get some leniency if you have a long track record of filing/paying on time. The First Time Abatement program, which help taxpayers avoid fees, is available to qualified applicants. Your tax preparer or the IRS can help you file for this.

This story was originally featured on Fortune.com