Stimulus check calculator: Confirm you received full relief payment before filing 2020 tax return

The Internal Revenue Service is essentially done sending stimulus checks, but if you didn't receive your fully promised payment, don't fret — there's a quick fix.

Americans who have not received their coronavirus stimulus check payments, or who received the incorrect amount, can claim the missing money when they file their 2020 tax return.

The CARES Act, passed in March, provided cash payments of up to $1,200 for adults ($2,400 for couples filing jointly) and $500 per child under 17. And the $900 billion coronavirus relief package, approved at the end of December, authorized additional payments of up to $600 per adult ($1,200 for couples) and up to $600 for each qualifying child under 17.

The first check was based on either your 2018 or 2019 tax return, while the second check was based on your 2019 return. But in some instances, Americans either didn't receive the stimulus check, or didn't receive the full amount they were entitled to, given instances like job losses or the birth of a child.

Millions of Americans lost their jobs, or saw their income reduced, this year as a result of the pandemic -- meaning that many individuals who didn't initially receive the money based on their 2018 or 2019 tax returns may now qualify.

FILE - A banking customer withdraws money from a ATM machine in Santa Fe, New Mexico. (Robert Alexander/Getty Images)

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If you think the IRS owes you stimulus money, you can use a recovery rebate worksheet to calculate how much you should receive and claim that amount on Line 30 on your 2020 tax return. The IRS will include your stimulus payments as part of your refund check.

You can use this free stimulus check calculator from Omni to determine how much money you should have received from the first payment, and use this calculator to see how much you should have received from the second payment.

If you received the incorrect amount of money, you can still receive the full payment: To do so, you need to file a 2020 tax return and claim a Recovery Rebate Credit.

The IRS opened up Free File, free online tax preparation software, for taxpayers who earn less than $72,000 to prepare and file their income tax returns. Americans can also claim their stimulus check using the tool.

"For 2021, eligible taxpayers who did not receive the full amount can claim it as the Recovery Rebate Credit when they file their 2020 tax return," the IRS said. "Use IRS Free File to file and claim this important benefit."