Almost 1 million people are about to lose their tax refunds from 2021 -- including a stimulus check in the form of the 2020 recovery rebate credit -- simply because they didn't file a tax return. The average tax refund in 2021 was $2,815, which is a lot of money to give the government.

According to the IRS, almost 940,000 taxpayers have unclaimed refunds from 2020. If you're one of the many taxpayers who never claimed their 2020 refund, you don't have much time left to act. By law, the IRS keeps these unclaimed tax refunds for three years. The agency usually transfers the money to the US Treasury after the deadline passes to claim your refund. 

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Usually, taxpayers have three years from the end of the tax season when they didn't claim their refund, but this year is a bit different. Back in 2021, the deadline to file your taxes was extended until May 17, 2021, and that means that you have until May 17, 2024 if you want to claim any missing money. 

Online tax software can help you complete your tax return to claim a tax refund for 2021 (you can also use your phone to scan your important tax documents), but you can't file 2020 returns electronically. You must file prior-year tax returns on paper. To do that, you'll need to print and mail your 2020 tax return for 2021 to a specific regional IRS office, depending on where you live.

Read on to learn about how to claim your 2021 tax refund, including what to do if you're missing old forms and where to mail your 2020 tax return.

For more, if you're still waiting for this year's refund, here's how to track the status of your refund.

When is the IRS deadline to claim a tax refund from 2020?

By law, the IRS is required to hold on to unclaimed income tax refunds for three years, and filers have a three-year window from the original due date to claim their refunds. If you don't file to claim your tax refund after three years, the money becomes the property of the US Treasury, and you won't be able to get it back.

What is the due date this year? Back in 2021, the IRS extended the tax deadline from April 15, 2021 to May 17, 2021, due to continued financial strain from the COVID-19 pandemic, so if you want to claim your missing money, you'll need to file 2020's return by May 17, 2024. 

Since tax returns for prior years cannot be filed electronically, you'll need to ensure that your 2021 return is addressed to the proper IRS regional office and postmarked by that May 17 date for most taxpayers. 

What is the Recovery Rebate Credit? 

Think back to 2020 and 2021 -- you'll likely remember the three economic impact payments, more commonly known as stimulus checks, that were sent out. While many received the full amount of their economic impact payments, it's possible that you could be missing all or part of one or more of those payments. 

Enter the recovery rebate credit. If you missed one or more of your economic impact payments or didn't get the full amount you were owed, you could have indicated this on your 2020 and 2021 tax returns, and the government would pay you the money you were owed. If you missed out on all or part of your stimulus check payments in 2020 and you didn't file your 2020 tax return, you have until May 17, 2024, to claim your missing money. If you only missed out on 2021's Economic Impact Payment and didn't file your 2021 return, you have until April 15, 2025 to file your return and claim your missing money.

How can I find out if the IRS has an unclaimed tax refund for me?

There's no easy way for taxpayers to discover whether or not they're missing tax refund money from 2021. The only way to learn if the IRS is holding an old refund for you is to file a return for that year.

The IRS Where's My Refund tool can't help; it only reports the refund status of those who've already filed their taxes.

You can find out the amount of your missing recovery rebate credit. According to the IRS, you'll need the tax years and amounts of the economic impact payments you received so you can calculate your recovery rebate credit. After you've found the necessary information, you can either plug the information into your tax preparation software of choice or you can use the Form 1040 Recovery Rebate Credit Worksheet to calculate how much you are owed. 

To find the amount of your economic impact payments, you can either check your IRS online account or one of the several mailed notices the IRS sent with the amounts of the payments. The mailed notices are Notice 1444 (for the first Economic Impact Payment which was delivered in 2020), Notice 1444-B (for the second Economic Impact Payment which was delivered in 2020) and Notice 1444-C (for the third Economic Impact Payment delivered in 2021). 

How can I claim my 2020 income tax refund from the IRS?

To claim a refund for 2020, you will need to submit your 2020 tax return through the mail. Most tax software publishers keep their prior years' software available for three years. Tax software can help you complete IRS Form 1040 and all the other required forms and schedules, but it cannot e-file for you. You'll need to print, sign and properly address the printed tax return, which needs to be postmarked no later than May 17, 2024 for most tax filers.

To file an old 2020 tax return, you'll need to mail it to a specific regional IRS center listed on the last page of this year's IRS Form 1040 instructions (these instructions are from last year's filing season, but the addresses of the regional IRS centers are still valid). The address you need to use depends on the state or US territory in which you live.

The IRS notes that the agency may continue to hold your 2020 tax refund if you have not filed tax returns for 2021 and 2022.

What documents do I need to file my 2020 income tax return?

You can find the tax forms for 2020 on the IRS forms page. If you're missing a W-2, 1098, 1099 or 5498 from 2019, the IRS recommends you request a copy from your employer or bank.

You can also order a free wage and income transcript from the IRS and then use the information from the transcript to file your tax return. To download an instant transcript, you'll need to create an online IRS account if you don't already have one.

Can my unclaimed refund be kept by the IRS to cover tax debt?

If you think you were due a refund from 2021 but you don't receive one after you file your old tax return, all or part of your tax refund may have been offset, meaning it was used to pay past-due federal tax, state income tax, state unemployment compensation debts, child support, spousal support or other federal debts such as student loans.

Tax refund offsets that cover past-due federal taxes are managed by the IRS, and you should receive a notice from the agency explaining the offset. All other refund offsets are handled by the Bureau of Fiscal Services' Treasury Offset Program, which should also send you a notice if your tax refund was used to pay debts.

If you don't believe you owe back federal taxes and receive an offset notice from the IRS, you can call the agency at 800-829-1040 for more information. For all other debt-related tax return offsets, you can call the Treasury Offset Program at 800-304-3107 to find out more details.