The Internal Revenue Code of the United States requires that the dependent child be under the age of 17 to be eligible for the Child Tax Credit.  If age 17 or older and and a dependent they are eligible for the $500 Other Dependent Tax Credit.

" Doesn't seem fair. "    This often comes as a shock to parents with the first child to turn 17.  Congress wrote the tax law that way, so in the year the child turns 17, you lose the child tax credit.  They used the same criteria to determine whether you would receive a stimulus check for a dependent child.  You could only get the $500 stimulus for a child who was UNDER 17 in 2019.