Even if you claim them as a dependent they might still need to file their own tax return. Be sure on their return they check the box that says they can be claimed on someone else’s return. If their only income is W2 and under 12,400 they do not have to file a return except to get back any withholding taken out.
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-
dependent/00/26111
If one is under 19 on December 31 you can claim them no matter how much they made. But if they are 19 or older you can only claim them if they were a full time student or made less than 4,200 total for the year.
