We had a baby in June, we are not married and are filing separately. Who should claim the baby on their taxes?

Are you living together ?

If so, the one who would benefit the most from using the deduction.
Figure your taxes both ways, which way would you both get the most money back.

Agreed!

In case of unmarried parents, the IRS rules for divorced or separated parents apply for claiming the child.
Only the custodial parent can claim the child. Non custodial parent can claim only when custodial parent signs a declaration to allow non-custodial parent to claim the child.

MukatA:

Your post is accurate if the tax exemption is not specifically address in the divorce or separatiuon agreement.

If it IS addressed, the IRS will follow what the divorce agreement says.