One or the other (but not both) of you can claim your son for all the child tax benefits. The two of you must decide which of you will claim him. Total tax benefits may be better for one or the other to claim him. Whoever paid more than half the costs of maintaining your home, could file as Head of Household if they claim the son as a dependent.
Whoever claims the son might also qualify for EIC and child tax credit or additional child tax credit. The only way to know which is best for both of you combined is for each of you to see what your tax situation would be if you claimed him and if you didn't claim him.
