ORS § 419B.406
When a child or ward is in the legal custody of the Department of Human Services and the child or ward is the beneficiary of an order of support in a judgment of dissolution or other order and the department is required to provide financial assistance for the care and support of the child or ward, the state is assignee of and subrogated to the child or ward's proportionate share of the support obligation including sums that have accrued whether or not the support order or judgment provides for separate monthly amounts for the support of each of two or more children or wards or a single monthly gross payment for the benefit of two or more children or wards, up to the amount of assistance provided by the department. The assignment shall be as provided in ORS 412.024.
ORS 419B.406