In this child support proceeding, father appeals from a judgment amending his child support obligation. The state concedes that the trial court erred. We review de novo, ORS 19.415(3), accept the state’s concession, and reverse and remand.1

Father first assigns error to the trial court’s rejection of a collateral attack on a prior stipulated judgment establishing paternity. Father has failed to establish the necessary requisites for setting aside a stipulated judgment, and we reject his arguments without further discussion.

In his second assignment of error, father argues that the trial court erred in determining the amount of his support obligation. The state concedes that the trial court incorrectly calculated father’s child support obligation. We accept the state’s concession that, in this case, the trial court erred in considering a third-party’s income in calculating father’s support obligation as a noncustodial parent.

Reversed and remanded.