How to File a Tax Extension (IRS Form 4868)

There are three ways to get the extension, and they are not equally sensible.

1. Pay online and tick the box. Make any payment through IRS Direct Pay and mark it as an extension payment. No form at all.
2. File electronically. IRS Free File will file Form 4868 for you at any income level, and most tax software does it free.
3. Mail the paper form. Fill in Form 4868, post it before the deadline.

The first one is the least work by a distance. The rest of this covers the paper form, because that is the version worth understanding, and comes back to the online route at the end.

Read the title of the form: Application for Automatic Extension of Time To File.

That word does real work. You are not asking permission and there is no decision being made about you. File it on time and correctly and the extension is granted, every time. You do not give a reason, you do not explain yourself, and nobody at the IRS reads it and judges.

It moves your filing deadline six months, from April 15 to October 15.

Line 1 is your name as it appears on your tax return. Filing jointly? Put both names here, in the same order they appear on the return.

Grab the form itself from IRS.gov. Search for Form 4868 and take the current year's version, because it is reissued annually.

Street address, then city, state and ZIP on the line below.

Use the address where you will actually receive post. If the IRS needs to tell you something about this extension, that is where the letter goes.

Your nine-digit SSN goes on line 2.

This is the field that connects the extension to you. Get a digit wrong and the IRS cannot match the extension to your return, which means as far as their system is concerned you never filed one.

Filing jointly? Your spouse's Social Security number goes on line 3.

Filing separately changes this completely: leave line 3 blank, and your spouse files their own separate Form 4868. One extension does not cover two separate returns.

Line 4 is where people get stuck. It asks for your estimated total tax liability for the year, and it is asking before you have done the return.

Estimate it properly rather than guessing. If you are employed, your W-2 withholding is a reasonable starting point. If you are self-employed or on 1099 income and have not made estimated payments, work out roughly what you owe on the year's profit, because it is likely to be a lot more than you expect.

A rough estimate made in good faith is fine. Leaving it blank or writing an obviously invented number is what causes problems.

Line 5 is the total you have already paid in for the year: withholding from your pay, plus any quarterly estimated payments.

Line 6 is line 4 minus line 5. That is your balance due, the amount you are still short.

Line 7 is the amount you are sending with the extension. It does not have to equal line 6.

Here is the part that matters most on this whole form: you can put zero here and still get the extension. The extension is never conditional on payment. But any unpaid balance starts accruing the failure-to-pay penalty and interest from April 15, so pay as much as you can manage.

Lines 8 and 9 are two checkboxes for narrow cases: being out of the country, and filing Form 1040-NR. Almost everyone leaves both empty.

Form 4868 has no single address. Page 4 carries a chart, and you find the row for the state you live in.

Posting it to the wrong service centre means it may not be processed in time, and a late extension is no extension.

Each state has two addresses in that chart, and this is the detail most people miss.

One column is for when you are enclosing a cheque, the other for when you are sending the form alone. They are different IRS service centres in different states. Read across to the correct column, not just down to the correct row.

If you are enclosing payment, make the cheque payable to the United States Treasury and write your Social Security number and "Form 4868" with the tax year on the memo line.

Go to IRS Direct Pay, choose to pay from your bank account, select extension as the reason for payment and pick the tax year.

That is it. Making an extension payment electronically grants the extension on its own and you do not file Form 4868 at all. The confirmation number is your proof.

It takes about three minutes, costs nothing from a bank account, and removes every way the paper route can go wrong: no wrong address, no postmark race, no lost envelope.