Gore v. Gore
In Gore v. Gore, 169 Ariz. 593, 821 P.2d 254 (Ariz. 1991), the Court of Appeals of Arizona considered whether a father's child support obligation could be extended beyond his son's 18th birthday, until his graduation from high school. Id.
The support extension/modification was sought pursuant to a change in Arizona law that became effective after the divorce of the parties. Id. at 256.
Holding that the amendment could be applied to modify the existing child support order, the court explained:
A statute is considered retroactive when it affects a vested right. Child support payments become vested upon the due date of each payment; each installment "is in the nature of a final judgment conclusively establishing the rights and duties of the parties to that installment."
Thus, appellee's right to cease making child support payments on the child's 18th birthday was not a vested right until the child's 18th birthday.
Accordingly, as the statute extending the duration of child support payments was enacted long before the child's 18th birthday, it does not require retroactive application. Id.