Sirs,
I am married filing jointly. In 2023 a child graduated college, then lived at home through August 2023. I fully supported him through August. He then went on active duty military and earned just above the amount required to file taxes independently.
According to the 2023 1040 Instructions, pages 17-19, my child meets all of the qualifications as a dependent. Page 10 of the Instructions, Chart B, specifically address those dependents who still have to file. My child meets the requirement for a single dependent (he is unmarried). None of the items in Chart C on page 11 apply.
I received a letter from the IRS that I had claimed a dependent that filed their own taxes? Why would they question this? I am sure I followed the instructions exactly.
I suggest you speak with your son, it sounds like he filed and claimed himself (as a non-dependent).
A dependent that is claimed by another taxpayer cannot also file and also claim themselves.
Did your son file a tax return of his own for 2023 on which he said no one could claim him as a dependent? Ask him? If he said that on his own return and then you claimed him as a dependent, you are both going to get letters so the IRS can sort out whether you could have claimed him.