ORS § 545.355
When an irrigation district under contract with the United States has levied any assessment for collection of money payable to the United States under the contract, if the Secretary of the Interior has, by agreement with the board of directors of the district, authorized the extension or cancellation of any payments due the United States by the cancellation of assessments already levied but remaining unpaid, the board of directors shall certify to the tax collector of the county in which the land is located a statement of the year and amounts assessed against each tract for which cancellation has been authorized. The tax collector upon receipt of the certificates shall, if the assessment remains unpaid, indorse upon the district's assessment roll, "Corrected under certificate of board of directors," and deduct and cancel from the assessment against each tract the amount of the assessment authorized to be canceled.
ORS 545.355