My ex-wife and I have a custody agreement in which we alternate years on claiming our daughter (12). The expanded child tax credit for 2021 ultimately will be tied to the 2021 tax filing year in which I will claim my daughter, but the payments are based on the latest filing year (2020) in which my ex-wife claimed my daughter. Should she defer the payments with the IRS as to not risk having to pay this money back when she files her 2021 taxes? I have looked at other online forums and articles and information is very vague.
a custody agreement is worthless from an income tax perspective. the tax laws say only the custodial parent can claim the dependent unless they furnish the non-custodial parent with a signed and dated form 8332 (for 2021). the non-custodial parent must include the form with their income tax return. to enable the NC parent to e-file, form 8332 can be mailed in with form 8453 while the rest of the return can be e-filed. be sure to read the filing instructions for form 8453 once the 2021 forms are available.
Your wife can unenroll at the IRS web site.
Unfortunately, the function that would allow you to enroll your child to get the advance payments in your name is not available yet. The credit will be reconciled on your tax return and if you claim your child as a dependent, and did not receive the full amount of the advance payment, you will get the credit on your return. The advance payments don't change the amount of the credit, just when it is paid.
In order to claim the child as a dependent, the child must live with you more than half the nights of the year, or if the child lives with the other parent more than half the nights of the year, the other parent must give you a signed form 8332, which you must mail to the IRS after e-filing. The full rules are here,