If you missed one of the first advance child tax credit (CTC) payments, you may be able to get catch-up deposits through the end of the year, according to the Treasury Department.

The first two enhanced CTC payments — which are worth up to $300 for children under 6 and $250 for children aged 6 to 17 each month through the end of the year — were sent out on July 15 and August 13; the third will go out next week.

Most eligible households don't have to do anything to get their checks. Taxpayers who filed an income tax return in 2019 or 2020 and claimed an eligible child, or who signed up to get a stimulus check last year and had an eligible child, should have gotten their first two CTC payments automatically.

But the IRS does not have information for everyone who is eligible. Those that didn't get a payment have a few ways to sign up for the payments going forward: Low-income families who don't usually file can use a website created by Code for America and the Treasury Department to submit a simplified tax return. Other families will be able to use the IRS' Child Tax Credit Update Portal to update bank account and mailing address information.

Initially, the IRS said that catch-up payments would likely be made next tax season. But Treasury says those that update their information now may receive increased monthly payments to catch up, through the end of the year.

Around 4 million children in the poorest families are at risk of not getting the payments, according to a recent report from the Center on Budget and Policy Priorities. Signing up now will ensure that they get the advance deposits.

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Don't miss: Use this online tool to sign up for the $300-per-month child tax credit