The IRS has rules and regulations for who gets the dependent deduction. According to IRS regulations for who claims the kids, the custodial parent is defined as the parent who has the children for the greater portion of the year and thus is the only person entitled to make the deduction. A judge can order a custodial parent to sign a declaration allowing the other parent to take the exemption, but if this declaration is not signed, then technically, the deduction is not allowable under IRS rules. If the declaration is offered and signed, then the loss of the exemption should be entered into the calculation of child support resulting in a higher amount for the paying parent. If custody is 50/50, (and I mean truly 50/50 – because most joint custody agreements never actually work out to really 50/50), then the alternating year deduction make sense. Otherwise, a custodial mom should think twice about giving up her rights to the tax deduction.