It's Tax Day. Here's what time your return is due - and how to file for an extension.

Andrew Keshner

For many taxpayers, it's still possible to get free last-minute tax prep in time for the April 15 deadline.

The April 15 tax-filing deadline is here, and the sprint is on for millions of people who still need to submit their income-tax returns.

The Internal Revenue Service received 101.8 million tax returns through early April , and it's expecting nearly 129 million returns in total to be filed by Tax Day. Taxpayers have until 11:59 p.m. in a taxpayer's time zone on Monday to get their return filed.

The agency also expects more than 19 million requests for extensions this year. An extension gives people an Oct. 15 deadline to file a return - but it doesn't give them additional time to pay any taxes they owe.

The final push to file tax returns or get an extension is a perennial feature of tax season. But a new series of studies, one of which examined participants' behavior around filing tax returns, sheds light on why some people wait until the last minute.

When people focus more on the negative aspects of an upcoming task than on its positive parts, they tend to put it off, according to Russell Fazio, a psychology professor at the Ohio State University and co-author of the study.

And the tax-filing process is ripe for stalling. After all, it's "a task that can be unpleasant, confusing and time-consuming," said Fazio, who conducted the study with Javier Granados Samayoa, a University of Pennsylvania postdoctoral fellow and former Ohio State grad student.

People who usually latched onto the negative side of an upcoming event also tended to be more likely to say they filed their taxes in the first two weeks of April, the authors determined in the study, which was published in March. They saw that trend even in a pool of people who expected refunds.

Unfortunately, the IRS still expects people to file returns - no matter how they feel about doing their taxes.

"If you leave it to the last minute, you're making the situation all the more difficult for yourself," Fazio added.

For all the procrastinators out there, here's a guide to making the next couple of days a little less daunting.

When are tax returns due?

For most people, the end of the day on April 15 marks the deadline to pay any owed tax bill and file a 2023 tax return. It's also the last date to turn in an extension request before penalties and interest apply.

Because of calendar quirks for the observance of state holidays, taxpayers in Maine and Massachusetts have an April 17 deadline. Taxpayers impacted by disasters also have their own timelines. After wildfires in Hawaii, for example, certain residents and businesses in the state now have an Aug. 7 deadline.

Electronic filing is the best and quickest way to send returns to the IRS. But what if you e-file a return at the very last minute on April 15 and the IRS rejects it because of an error?

You're in luck: The agency gives people a small grace period of extra time to fix the problem, according to Mark Jaeger, the vice president of tax operations at TaxAct, a company that makes tax-preparation software. The IRS will still count the return as being on time if you successfully correct the error within the allotted time, he said.

This "perfection period" lasts five calendar days, the IRS says, making April 20 the date to watch. One example of a fixable glitch might be a mixed-up identification number for the employer paying wages, Jaeger said.

How do I apply for an extension on my taxes?

The IRS penalizes people who don't pay their bills on time, as well as people who don't file their returns on time.

But the failure-to-file penalty is steeper, amounting to 5% of the unpaid taxes for each month or partial month a tax return is overdue, up to 25%. The failure-to-pay penalty is 0.5% of the owed amount. If someone gets hit with both penalties, the late-filing penalty would be 4.5% and the late-payment penalty would be 0.5%, for a 5% combined penalty each month after the due date.

After 60 days, a late filer would be paying a penalty that's either the whole size of the unpaid tax or $485, whichever amount is less. The penalty for late filing maxes out after five months, but the late-payment penalty will continue up to 25%. Combined, the maximum penalty for past due taxes and an unfiled return is 47.5% of the unpaid tax, plus interest. The IRS currently assesses an 8% interest rate on penalties.

Getting an extension avoids the failure-to-file penalty.

There are a range of ways to apply for an extension using Form 4868, including through tax software and the IRS Free File program, the agency's partnership with software providers. The IRS's own Direct File platform doesn't support extension requests.

IRS payment portals allow users who think they'll owe taxes to pay and select the extension field without filing a separate extension form.

There's generally no failure-to-file penalty attached to a late return when a refund is due, according to the IRS. Still, it's a good move for people to file an extension either way, an IRS spokesman said - after all, it's not worth risking a late-filing penalty if they learn after getting their return together that they owe taxes.

People have three years from the filing deadline to submit a return claiming a refund. After that, unclaimed money goes to the Treasury Department.

Read more: The deadline to receive 2020 stimulus-check money is fast approaching. Here's how to finally get yours.

It's fine to get an extension and still file by April 15, added Stephanie Sommers, the president-elect of the Accounting and Financial Women's Alliance, a professional organization.

"Filing for an extension simply provides you with additional time if needed, but it doesn't prevent you from filing earlier if you're ready," said Sommers, who is also the director of GMS Surgent, an accounting and advisory firm in Devon, Pa. "It's a flexible option designed to accommodate varying circumstances."

How do I pay any taxes I owe?

The IRS offers a range of payment options and accepts both full and partial payments. Its Direct Pay service lets users pay taxes directly from their checking or savings account.

The agency also accepts payments via credit card, debit card and digital wallets connected to platforms like PayPal (PYPL) and Venmo. However, third-party payment processors assess fees for people who go this payment route.

People who cannot pay their full bill before April 15 can slice it into smaller payments over time. For taxpayers who need a little extra time to pay the full amount, a short-term installment plan lets them pay it off in 180 days or less. There's no setup fee, though penalties and interest apply. This plan works for people who owe less than $100,000.

For people who need more time, there's a long-term payment plan. That carries a start fee of $31 for automatic withdrawals and $130 for non-automated payments. The long-term plan works for people who owe less than $50,000.

If you owe federal income taxes, there's a chance you also owe state income taxes. If you don't have enough money to pay both bills, devote as much effort as possible to paying off one, said financial adviser Rob Burnette, the CEO of Outlook Financial Center in Troy, Ohio.

"Don't carry two bills," he said.

People should also consider state-specific penalties and fees that apply to tax debts. "The IRS generally imposes higher penalties and interest rates for unpaid federal taxes compared to most state tax agencies," Sommers said. "The IRS tends to be more aggressive in pursuing unpaid taxes compared to state tax agencies."

When in doubt, turning to a tax professional may be a good move, she added.

Where can I still do my taxes for free?

Commercial providers like TurboTax (INTU) and H&R Block (HRB) do offer free tax-preparation options, though these may only work for stripped-down, relatively simple tax returns. Of course, both brands can handle more complex returns, too - for a price.

There's also the IRS Direct File platform, a no-fee option that can also handle simple returns. The pilot program is available in 12 states: Arizona, California, Florida, Massachusetts, Nevada, New Hampshire, New York, South Dakota, Tennessee, Texas, Washington and Wyoming. It's quick and easy to use, according to some early user reviews.

After April 15, however, people can't file their taxes through Direct File. The sole exception is for Massachusetts taxpayers, who have until their own deadline on April 17.

Other no-cost options include the IRS Free File program, a public-private partnership that allows taxpayers with adjusted gross income of $79,000 or less to receive free online tax prep from certain tax-software providers. For eligible taxpayers, there is also free in-person help available through programs like the IRS Volunteer Income Tax Assistance program.

Rushing 'can lead to errors, missed deductions, incomplete information'

It's understandable that you might want to rush to beat the deadline. But hastily filing your taxes could mean you overlook tax breaks and credits that could have carved down your taxable income and tax bill.

When deciding how quickly to move these final couple of days, last-minute filers should think about the complexity of their return and consider whether they have all the needed information, Sommers said.

"Rushing to file taxes can lead to errors, missed deductions, incomplete information, increased stress, lost opportunities for planning and delayed refunds," she said. "It's best to take the time needed for accurate preparation."

And if you are working with an accountant, remember they are on deadline, too. The expectation they can drop everything to get back to a client may not be realistic, Burnette said.

"I'm accommodating fewer distractions than I normally would," he said. "I'll leave it at that."

(MORE TO FOLLOW) Dow Jones Newswires

04-15-24 0902ET

Copyright (c) 2024 Dow Jones & Company, Inc.