Legal Question in Family Law in Maryland

No. If he is not the custodial parent, both parents need to sign IRS Form 8332 (available on the irs.gov site) to legally establish which parent is entitled to claim the child on their tax return in any given year. Otherwise your daughter is entitled to the exemption. Of course, if they are still married they are probably paying more taxes collectively than they would if they filed a joint return. It sounds like he's no longer paying support, so if she wants to use the exemption she should let him know that she intends to do so.