I notice you say "a dependent age 14" and not "my child age 14".
To get the child tax credit (CTC)(max $2000), instead of the "credit for other dependents" (max $500), the child must be closely related to you. A common example, you cannot get the CTC when you claim your domestic partner's child as a dependent.
You can also not claim an unrelated child for the Earned Income Credit or claim your domestic partner or their children as a qualifying person for Head of Household filing status.
