If your child is age 17 or over, they will not be eligible for purposes of the Child Tax Credit. The child tax credit is up to $2,000 per qualifying child under age 17.
Taxpayers with dependents who don't qualify for the Child Tax Credit may be able to claim the Credit for Other Dependents. They can claim this credit in addition to the Child and Dependent Care Credit and the Earned Income Credit.
The $500 Credit for Other Dependents (aka “Family Tax Credit”) was signed into law as part of the 2017 Tax Cuts and Jobs Act. It is effective for tax years 2018 through 2025.
Click here for "What is the $500 Credit for Other Dependents?"
Click here for "Understanding the Credit for Other Dependents".
Click here for Rules for Claiming Dependents.
Click here for information on "What Are Dependents"?