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He was not claimed as a dependent on my tax return.   The issue is that I THOUGHT he could be claimed, so when I did HIS taxes, I selected “could be claimed as a dependent by someone else”.  
it was after his return was accepted that I did my return and found he could not be claimed.  

I went back into the software and CHANGED the status in TurboTax which resulted in a larger refund for our state.  However, it triggered NO CHANGE on the Federal and therefore did not trigger a 1040x.   What I’m asking is if I need to maybe fill out a 1040x by hand and have him mail it in?  Or does he not need to do anything because he wasn’t actually claimed as a dependent. 

I just need instructions. There is no one at the irs available to help and their help desk can only offer all the links I’ve already read.