It depends. If he answers that he did not receive any Advanced Child Tax Credit then he will receive the full credit. She will not have the child listed on her return and she will have to report what she received and then he will have to repay what she received on her return.
What I am not sure of is can he report the amount received on his return and receive the Refundable Child Tax Credit and then they would both have received one-half of the child tax credit.
I am not sure if the IRS is tracking the Child Tax Credit by social security numbers of the children or of the parent who received the Advanced Child Tax Credit.
The IRS has stated the following concerning this situation:
If a parent is receiving 2021 advance child tax credit payments and they shouldn't be, what should they do?
Parents who will not be eligible to claim the child tax credit when they file their 2021 tax return should go to IRS.gov and unenroll to stop receiving monthly payments. They can do this by using the Child Tax Credit Update Portal. Receiving monthly payments now could mean they have to return those payments when they file their tax return next year. If their custody situation changes and they are entitled to the child tax credit for 2021, they can claim the full amount when they file their tax return next year.
How a taxpayer's custody situation may affect their advance
