Only the custodial parent can claim the child care credit. The custodial parent is the parent that the child lived with for more nights during the year. If the child lived with Mom most of the time, Mom is the custodial parent. If Mom is the custodial parent, Dad cannot claim the child care credit, even if he claims the child as a dependent. It doesn't matter whether Mom claims the child care credit or not. Dad cannot claim the child care credit under any circumstances if he is not the custodial parent.