If he qualifies as your dependent he has to mark that on his return. He needs to Go to My Info click EDIT by his name
Then scroll down to #3 Can someone else claim you?
If he doesn't qualify as your dependent he will have to mail his return and you will have to amend your return to take him off.
Who can I claim as a dependent?
https://ttlc.intuit.com/community/credits-and-deductions/help/who-can-i-claim-as-my-dependent/00/267...
