Yes----you will be able to file a 2021 tax return in early 2022 in order to get the child tax credit for your children.  If you are getting the monthly payments now, you will receive the other half as a refund when you file your 2021 tax return.

Here is a link to information from the IRS----there is a lot of information to read if you use the additional links on the right side of the page

https://www.irs.gov/credits-deductions/2021-child-tax-credit-and-advance-child-tax-credit-payments-t...

If you did not get all 3 stimulus payments  then you will want to file a 2020 return to get them as well ... the first 2 will be on the return and the third is released when the 2020 return is processed.