The IRS is reminding taxpayers that they have until April 15 to file their 2021 tax return and receive a stimulus check. According to the agency, people who didn’t get the $1,400 pandemic relief checks in 2021 can still claim the recovery rebate credit.

“If you didn’t get the stimulus, you’re running out of time,” Syracuse University law professor Robert Nassau, who directs the school’s low-income tax clinic, told CNBC.

How will the IRS send the pandemic-era stimulus checks?

In December, the IRS said it would automatically send up to $1,400 to people who didn’t claim the recovery rebate credit on their 2021 tax returns. The agency said the payments would begin arriving by direct deposit in late January. Taxpayers can create an IRS account online to view their tax records and find out if a stimulus check was issued. About $1 billion in unclaimed refunds from more than 1.1 million taxpayers still remains, according to the IRS.

How can taxpayers send their 2021 tax return?

Nassau said people who are mailing their 2021 return should use certified mail to ensure it’s sent before the deadline.

“I’ve had situations where the IRS gets something after the filing [due] date, and they just reflexively say it’s too late,” Nassau said. “Spend the $5 and send it certified.”

There are also free options available to file taxes, but some services may not support electronic filing.

What is the 2021 stimulus check?

The 2021 stimulus check, authorized in 2021, is part of the American Rescue Plan, according to Newsweek. The IRS issued the checks to provide assistance to people financially impacted by COVID-19. However, some people may have missed the payments because they were unclear about their eligibility, the IRS said.

“Now that we are back in a COVID-type period, where tariffs loom and prices for essentials like food and personal care are soaring, an extra $1,400 can make an enormous difference, particularly for individuals and families who are already food insecure,” Lisa Perkins, a clinical professor and director at UConn Law Tax Clinic in Connecticut, told Newsweek.