My child did not turn 17 until December 2023. Do I still get a credit for her?

You lose the Child Tax Credit for the year in which the child turned 17, even if her birthday was on December 31.   Instead, you get the $500 credit for other dependents.   Remember that when she was born in late December--you got the CTC for that whole year, even though she was only with you for about a month.

Q. My child did not turn 17 until December 2023. Do I still get the Child Tax credit (CTC) for her, for 2023?

A. No.

But, back in 2006, you got a full year CTC even though she was with you less than a month. 

Since 2018 you get an (up to) $500 "Credit for Other Dependents", for those who do not qualify for the CTC.