You did not say what state you are in. There are only several states that recognize common law marriage. If they are not in one of those states they cannot file a joint return. "They recently married...." What does that mean--were they legally married as of December 31, 2018 or not?
STATES THAT RECOGNIZE COMMON LAW MARRIAGE
CO, DC, CO,IA,KS,MT,OK.RI,SC.TX, UT
And further--if your son files a joint return, then you cannot claim him as a dependent, nor can you claim the education credit.
**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.**
