Is my ex-boyfriend allowed to claim my daughter on his taxes?

Short version, if I understand your facts, "no."  In the absence of a court order stating otherwise, the parent with actual physical custody a majority of the time is entitled to claim a minor child as a dependent for exemption and other tax purposes. If this matter is disputed, it would be wise to consult a family law specialist, and to specifically provide for tax exemptions while dealing with formal orders of custody, visitation, and support.  On that last score, unless the father is unemployed, he should probably be paying a lot more than $100 per month in child support.  For the current guidelines, see the chart posted at http://willicklawgroup.com/child-support/.