The good news? Your stimulus check arrived. The bad news? It’s not for the amount you were expecting.

Last week the IRS released new guidance laying out a few of the reasons your check might be a bit leaner than what you were hoping for, noting that “some Americans may have received a payment amount different than what they expected.”

The primary culprits? The agency was relying on your most recent filing (which may differ from your information for the most recent year); you have added a dependent since your IRS information was updated; or your check was reduced owing to past-due child support or garnishments. As of last week the agency reported that it had “successfully delivered nearly 130 million Economic Impact Payments to Americans in less than a month, and more are on the way.”

What should I do if my stimulus check was less than expected?

There is a way to receive the correct amount—but you’ll need to wait until you file your 2020 return, says Nathan Rigney, lead tax research analyst with H&R Block’s Tax Institute. The IRS has already confirmed this will be an option, and Rigney guesses they will either add a line on the 1040 credits schedule where you will be able to apply the missing amount, or the agency will issue other instructions for how to claim the correct amount closer to next year’s filing deadline.

Rigney says there are a few different scenarios that could have led to an incorrect check amount.

The first is that you have not yet filed your 2019 returns, so the agency was relying on your 2018 information to calculate your check. If you have added a dependent since then, or if your income in 2019 was substantially different than in 2018, it would affect your total.

Another issue, says Rigney, is that for people who don’t normally have filing requirements, such as some veterans or Social Security recipients, the IRS would have calculated their checks based on their information alone but would not have had information if they had dependents to claim. So, for instance, if they had custody of a grandchild they should be able to file for the missing credit(s) in 2020.

Finally, in cases of divorce and shared custody, there may be confusion, as only one spouse is allowed to claim the credit.

Will my stimulus check count as income on my tax return?

No. The government stimulus payments are tax-free and will not count as income on your 2020 returns. However, if you feel your payment was for the wrong amount, Rigney recommends keeping any paper correspondence from the IRS, as well as any records that pertain to income and dependents in order to claim the correct amount on your 2020 return.

And, in the meantime, two bright spots to consider: Round two stimulus checks could soon be in the works, and the IRS has begun to add 3,500 phone operators to field inquiries from taxpayers with questions about economic stimulus payments and other tax issues.