TT mistakenly told me we could not claim my son as our dependent because I reported he lived with us 6 mos in 2018. In fact, he entered the Army in SEP. What to do?

[dubina666]

My return was rejected because my son indicated on his return that he could not be claimed as a dependent by someone else.  IRS didn't like that.  I corrected my return before I e-filed several days ago, and I told my son (who had previously filed his individual return) that he should correct  it (though I told him the correction might not matter).  He was busy with an Army training test so he didn't revise his personal info, and the IRS doesn't like one SSN being claimed by two or more people ... so my return was rejected.  Now I think he can change his personal info before Apr 20 to fix his problem and mine.

[DoninGA]

Your son would have to amend his tax return to change his dependency status to being a dependent from not being a dependent.  An amended tax return can only be printed and mailed, not e-filed.  The IRS will take up to 4 months to process the amended tax return, or longer.
Until he does that you will not be able to e-file a return with him as a dependent on your tax return.  After he files the amended return, you can only mail your tax return since the e-filed return will continue to be rejected until the amended return has been processed.

[Critter]

All you can do is mail in the return for this tax year and you do not need to wait for him to amend.