Congratulations on your child born in 2021! There will be a portal on the IRS site where in August or September you can enter information for a child who was born in 2021. You will need your child’s Social Security number. The portal is not ready just yet.
https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
https://www.irs.gov/credits-deductions/2021-child-tax-credit-and-advance-child-tax-credit-payments-t...
Any amount of the CTC you do not receive in 2021 will be reconciled when you file your 2021 tax return next year in 2022.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**