It is surreal to think that this time four years ago the world was shutting down and the COVID-19 pandemic was just beginning: 2020 was an unprecedented year when people were forced to change the normal mode of operation. Because of the collective trauma we were facing, some everyday things—such as doing your taxes—may have fallen through the cracks.

Now the Internal Revenue Service (IRS) is reminding those who have not filed their 2020 taxes that the May 17 extension to do so is quickly approaching.

An incentive for many to file is the opportunity for a refund. The IRS estimates that around 940,000 Americans are entitled to one, and that $1 billion in refunds is currently left unclaimed, with individual payouts averaging around $932. If Americans who are due a refund from 2020 don’t file, the money becomes the property of the U.S. Treasury.

IRS Commissioner Danny Werfel wants people to take advantage now. “There’s money remaining on the table for hundreds of thousands of people who haven’t filed 2020 tax returns,” he explained in a statement. “We want taxpayers to claim these refunds, but time is running out for people who may have overlooked or forgotten about these refunds. There’s a May 17 deadline to file these returns so taxpayers should start soon to make sure they don’t miss out.”

The pandemic extended the normal filing deadline. Historically, the cutoff was around April 15, but a grace period was added to the three-year rule. Details of the May 17 postponement were outlined in February of last year.

The unclaimed refunds might be larger than expected because of credits. Many taxpayers could benefit from the Recovery Rebate Credit, which came about due to the Coronavirus Aid, Relief, and Economic Security (CARES) Act. Those who did not receive the full amount due with the Economic Impact Payments (aka stimulus checks) can make up the difference here. An Earned Income Tax Credit is also available for eligible low- and moderate-income earners.

“People faced extremely unusual situations during the pandemic, which may have led some people to forget about a potential refund on their 2020 tax returns,” Werfel explained. “People may have just overlooked these, including students, part-time workers and others. Some people may not realize they may be owed a refund. We encourage people to review their files and start gathering records now, so they don’t run the risk of missing the May deadline.”

If the thought of filing 2020 taxes intimidates you, here’s how to break it down to small actionable steps. First, request documents such as a W-2, 1098, 1099, or 5498 from your bank and employers. If this isn’t an option, you can request an online transcript from the IRS using the agency’s free tool. Another option is to use Form 4506-T to request a hard copy “wage and income transcript,” but this will take more time.

There are some caveats about potential refunds. Money could be withheld if you also have not filed your 2021 or 2022 taxes. If you owe money for child support, student loans, or back taxes, the funds will first be applied there as well. High-income earners who have not yet filed will be receiving a letter in the mail.