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Stimulus check fine print: This is why you got the payment size you did

Why did the IRS calculate your stimulus check the way it did? We'll tell you everything you need to know about the under-the-hood equation.

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To truly understand why your stimulus check payment is what it is, you have to look at the math.

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You thought you were getting a stimulus check for one amount, but you got it for another. Why? It might be that the IRS owes you a "plus-up payment" for any missing money, there was a calculation error you'll have to triple-check with our $1,400 stimulus calculator or, simply, you didn't actually qualify for as much money as you expected. Some rules changed with the third check that could account for people being disqualified this time around. (Here's how to calculate your first and second stimulus checks.)

In general, the stimulus check law contains a formula that starts with your adjusted gross income and factors in the number of dependents you have. We'll explain how the IRS uses its formula to determine your total stimulus check amount and how it can be the difference between your family getting $5,600 or nothing at all. (Here's more information for people who don't file taxes.)

In addition, here's everything to know about other money that could be coming your way: the $3,600 child tax credit (calculate your payment total), $300 extra in unemployment payments, a $600 stimulus check for Californians and student loan debt forgiveness. Here's the latest on a fourth stimulus check.

Did the IRS use your 2019 taxes or 2020?

If you got a lot less money than you think you should have, the most likely culprit is that the IRS used your 2019 tax information to calculate your third stimulus check rather than your 2020 tax return -- which is officially due May 17. You can use an IRS tracker tool to see if the agency received and processed your 2020 return (and refund).

If the IRS owes you additional money, you'll be due a plus-up payment, which can take into account any change in your AGI and new dependents, including a new baby. We strongly suggest using our stimulus check calculator to ballpark how much you should expect, because the IRS won't tell you in its stimulus payment tracker.

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Stimulus check formula basics

The language of the March stimulus law provides the equation the IRS has to use to work out your total. Here are the major variables that plug into the formula:

  • Your AGI, taken from your 2019 or 2020 federal tax returns (or the last known information the IRS has on file.)
  • Upper income limits for single taxpayers, heads of household (for example, a single person with at least one child) and married couples filing jointly.
  • The number of eligible dependents you claim.
  • Reduction or "phase-out" rate -- the amount your total would drop for every $1,000 you make above the income limit that allows you to qualify for the full check amount. In other words, the IRS calculates a partial payment if you don't qualify for the full amount.
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Dependents can multiply your the total amount

Dependents of all ages count for $1,400 apiece toward your stimulus check total, which could cause it to soar, especially if there's a new dependent you can claim this year. That's the simple math of multiplying the number of dependents you have by a higher rate for each one.

However, there's a catch. With the previous two stimulus checks approved in March 2020 as part of the CARES Act and then in December, it was possible to get a partial payment even if you exceeded the maximum income limit -- if you had dependents

That's because the previous formula began with the largest amount you'd be eligible to receive (for example, $1,400 per single taxpayer or $2,800 for joint filers) and added $1,400 per qualifying dependent. Then it reduced the total possible sum according to your AGI and the phase-out rate.

It's a little like starting a test with a perfect 100 point score and subtracting a point for every question you miss, rather than starting with zero points and adding them all up at the end. But in this case, the dependents you name can start you at a higher value, say 110 points in our classroom example. So by the time you subtract "points," you may still get more than people who don't have dependents -- even if your AGI is above the maximum cap. The more child dependents you have, the higher your starting value and the higher your ending value, too.

That's no longer the case with the third stimulus check, so even if you had 10 dependents, you wouldn't get any money if you hit the income limit.

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Stimulus check calculations don't always make immediate sense.

Angela Lang/CNET

Strict stimulus check income targets this time

The third check is designed to target stimulus payments by setting a firm cutoff, which means that it would start by evaluating your AGI without the mitigating factor of your dependents. If you're over the limit, it wouldn't matter how many dependents you have. You still wouldn't be eligible for a check.

Stimulus check income limits


Full $1,400 per person maximum (based on AGI) Not eligible (based on AGI)
Single taxpayer Less than $75,000 $80,000 or more
Head of household Less than $112,500 $120,000 or more
Married couple filing jointly Less than $150,000 $160,000 or more

On the other hand, a family with a large number of dependents and an AGI within the boundaries could still receive a large partial payment, as long as they come in below that absolute upper income limit. You can experiment with our stimulus calculator for an idea of what you'd get.

Phase-out rate: Why this matters for stimulus checks

The phase-out rate, also called the reduction rate, is a key here, too. With the third stimulus check, there's a much more narrow income window that will allow you to receive a payment at all. 

For example, you're eligible for the full $1,400 amount if you earn under $75,000 a year (your AGI as a single taxpayer). You get a partial check for an AGI between $75,000 and $79,900, and no check at $80,000. That's only $5,000 of wiggle room in your income to qualify for a partial check or not. The higher you go over the $75,000 AGI, the less money you get, fast.

The phase-out rate means the difference between the first and third checks can feel start for someone in this narrow band between qualifying in full and just barely getting a check at all. Again, the more dependents you claim, the more money you'll receive in a third check.

For more information, brush up on stimulus check qualifications, what to know about reporting a problem with your stimulus payment and when it's time to file a payment trace with the IRS.