If you were the custodial parent for 2018 you are fine to claim him as your dependent. You already filed? If so and he messes up and enters the wrong answer for being claimed as someone else's dependent, then his e-file will be rejected. Then he will have to fix it and re-submit it. High school and college students make mistakes all the time with the question about being claimed as someone else's dependent.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
