The April 18 deadline for filing federal income tax returns is just over a week away. Taxpayers who think that they will not complete their returns on time may want to consider filing extensions.

A quirk of the calendar is giving taxpayers more time to file their returns this year. (The traditional filing day, April 15, falls on a Saturday, but the next Monday is a holiday in Washington, bumping tax day to Tuesday.)

Even with the extra three days, however, millions of taxpayers will not file on time — whether because of simple procrastination, or because they are missing critical forms. Last year, 13 million taxpayers requested extensions, the IRS said.

Filing for an extension is easy. Melissa Labant, director of tax advocacy with the American Institute of Certified Public Accountants, said almost anyone could get an automatic, six-month extension to file by filling out and submitting Internal Revenue Service Form 4868. Requests, unlike those in years past, require no explanation, she said.

While getting an extension is simple, tax experts emphasized a cardinal rule: An extension buys more time to file your return, but you still must pay any taxes you owe by the initial deadline.

“It’s an extension of time to file, not to pay,” said Bernadette Antonelli, an enrolled agent with Arlington Tax in Kearny, N.J.

Enrolled agents are federally licensed tax preparers.

If you owe taxes and do not pay by the filing deadline, you will be subject to penalties and interest. So if filers think they will owe money, they should estimate the amount the best they can, Antonelli said, and make the payment when they file for the extension.

“They need to rough out a tax return,” she said, “and approximate what they owe.”

While you are at it, be sure to round up, Labant said. Better to overpay and get money back later than to underpay and have to pay extra cash in penalties.

“When in doubt,” she said, “pay more, to avoid an underpayment penalty.”

Since you have to pay anyway when filing an extension, you really should try to file a timely return, especially if you have the necessary documents in hand, said Lisa Greene-Lewis, a tax expert with the do-it-yourself tax filing software TurboTax.

Last tax season, she said, about three-fourths of filers received refunds, which averaged about $2,800. You cannot claim your refund until you file, she said. So why wait?

“I’d suggest that people try to file, if they can,” she said.

One reason to seek an extension is missing important forms.

Often, for instance, people don’t receive Schedule K-1 forms, which report income from investments such as limited partnerships, until after the traditional filing deadline.

This year, the deadline for distribution of K-1 forms was moved up, so that may prove less of a problem, Greene-Lewis said.

A missing W-2 form is also a hurdle that may justify an extension. If you do not receive one, you can try to obtain it online — TurboTax offers automatic downloads from many employers — or call your employer to request a copy.

You can also request a transcript of the form from the IRS, Greene-Lewis said, but at this point you may not receive it in time for the filing deadline.

 

Ann Carrns writes for the New York Times.