Child support arrearage calculation; MCL 552.603; Clarke v Clarke; Malone v Malone; Retroactive modification; MCL 552.605c; Conversion of weekly amounts into monthly amounts; 2025 Michigan Child Support Formula (MCSF) 4.06(A); Determining daily amounts; 2025 MCSF 4.06(B); State disbursement unit; MCL 400.236(1) & (2); Friend of the Court (FOC); Michigan State Disbursement Unit (MiSDU); Michigan Child Support Enforcement System (MCSES)

Holding that the trial court erred in calculating defendant-father’s child support arrearage, the court reversed and remanded. Plaintiff-mother obtained an ex parte interim child-support order in 1988. A later Notice of Arrearage stated defendant had $2,100 in arrearages due. After a temporary support order was entered, the parties divorced in 1989. The judgment provided that all accrued support arrearages were preserved, and set child support at $420 a week. A second 1989 Notice of Arrearage showed that $28,980 had accumulated. In 1990, an order entered in the Virgin Islands where he was living with the two older children ordered defendant to pay plaintiff $350 a month in child support for the youngest child. The parties then agreed to a modified divorce judgment. Before 1999, he paid plaintiff a total of $8,011 in child support, and made no other payments until 2023, when a MCSES report listed a remaining “Payee Balance” of $70,935.64 and a “State Balance” of $2,642.50. The order at issue on appeal calculated that he owed plaintiff $8,774. It “did not mention the ex parte support order, the notices of arrears, the divorce judgment’s preservation of arrears or provisions for custody and support for all three children, or the amounts of total arrears calculated by MCSES or MiSDU.” The original judgment fixed the arrearage amount due before its entry, and “could not properly be retroactively modified.” The only event that could establish the date from which a new amount would apply was the filing of “a petition for modification.” But defendant did not file one “while the support payments were being assessed.” Thus, the support agreement provisions controlled. The rate before the judgment was the same it later set, $420 a week, which was owed from 8/31/89 to 5/31/90. From 6/1/90 to 12/9/90, the Virgin Islands order assessing $350 a month was in effect. The modified judgment with that amount then took effect. The court also found that the trial court erred in calculating the end of the youngest child’s time with plaintiff, in subtracting the amount due to the state from the amount due to plaintiff, and to the extent “it adjusted defendant’s obligation to account for where the children were living at the time.” He had to act “while the payments were being assessed if he wished to change the support order on” that basis.