In Birnstihl v. Birnstihl, the Arizona Court of Appeals reversed the family court’s dismissal of a petition to modify child support and held that claim preclusion does not bar modification when the basis to modify is correction of information a previous order used to calculate support.

When the parties divorced, Father was ordered to pay $1,850 in monthly child support. A few years later, Father filed a simplified petition to modify child support based on their oldest child’s emancipation and changes to the parents’ incomes.

The simplified procedure allows a parent to modify child support without a court hearing unless the other parent disputes the modification and requests a hearing within twenty days of service.

Mother did not request a hearing or file any type of response, so the family court modified child support. Ten days after the family court entered its order, Mother requested a hearing and filed a counter-petition to modify child support. The court never ruled on Mother’s untimely requests.

Subsequently, Mother retained an attorney who filed a motion to correct the child support order under Rule 85(C). Mother’s motion argued that child support was calculated based on incorrect figures for Father’s income and parenting time. Mother also filed a separate petition to modify child support where she reiterated that Father previously provided inaccurate information the family court used to calculate support.

Father filed a motion to dismiss where he argued that Mother’s failure to request a hearing barred her arguments. The family court dismissed Mother’s petition, finding it did not “allege a sufficient ‘showing of changes circumstances that is substantial and continuing’” pursuant to A.R.S. § 25-503(E).

Mother filed another petition to modify child support using the simplified process and attached Father’s tax return to prove he earned more than he claimed in his petition to modify. Again, Father successfully moved to dismiss Mother’s petition.

On appeal, Mother argued that her petition where she included Father’s tax return was sufficient to show a substantial and continuing change to modify child support.

Father essentially argued that because no circumstances changed since the family court modified child support, Mother’s petitions were correctly dismissed.

The Arizona Court of Appeals rejected Father’s contention and held that “changed circumstances” in child support context may be that incorrect information was used to calculate a previous order.

The decision cited the Arizona Child Support Guidelines, which permit a parent to modify child support when application of the Guidelines “results in an order that varies 15% or more from the existing [child support order].” A fifteen percent variation is considered evidence of substantial and continuing change.

In this case, if the family court used Mother’s evidence to correct Father’s income and parenting time, the resulting change would be greater than fifteen percent and therefore a sufficient basis to modify child support.