More than 9 million households will get correspondence from the government detailing 2021 tax benefits they qualify for but did not claim on their federal income tax return last year. That could be one of many COVID-era stimulus efforts, like the 2021 Recovery Rebate Credit (the third and final stimulus check), the Earned Income Tax Credit, or the enhanced Child Tax Credit.

Most of the letters are being sent to people who “appear” to qualify for the tax credits and rebates but did not file a 2021 return at all.

“Even if they aren’t required to file a tax return, they may still qualify for several important credits,” said IRS Commissioner Chuck Rettig in a statement. “We don’t want people to overlook these tax credits, and the letters will remind people of their potential eligibility and steps they can take.”

The missing tax benefits stem from last year’s American Rescue Plan Act, a COVID-relief bill that increased the Child Tax Credit from $2,000 to as much as $3,600, made it fully refundable, and made half of it payable in advance. The bill also allowed for a third stimulus check worth up to $1,400 for qualifying taxpayers and each of their dependents. 

Crucially, many of those benefits were available to people who don’t normally file a tax return—typically because they are low income—but they would have needed to file a return last year or update the IRS.

Those who didn’t claim their tax relief can still do so by filing a federal tax return now. There is no penalty for doing so, and the IRS’s Free File form is staying open for an extra month—through Nov. 17—to allow them to do so. Individuals with income below $12,500 and couples with a joint income below $25,000 may be able to file a simple tax return to claim the missing stimulus payment and Child Tax Credit.

The enhanced Child Tax Credit was especially beneficial for low-income families. Food insecurity dropped significantly, and helped lead to a record drop in child poverty, according to the U.S. Census Bureau. The stimulus payments also kept millions of people above the poverty line in 2021, according to the Urban Institute.

Claiming the COVID relief does not affect a filer’s ability to receive other governmental assistance, such as Supplemental Security Income, Supplemental Nutrition Assistance Program benefits, or Special Supplemental Nutrition Program for Women, Infants, and Children benefits.