Oregon Revised Statutes Revenue and Taxation § 308.335

(1) The Department of Revenue, upon its own volition or at the request of the county governing body, may examine and test the work of county assessors at any time, and shall have and possess all rights and powers of such assessors for the summoning of witnesses and examination of persons and property, and for the discovery of property subject to taxation.

(2) If the department ascertains that any taxable property is omitted from the assessment list, or not assessed or valued according to law, it shall bring that fact to the attention of the assessor of the proper county in writing. If the assessor neglects or refuses to comply with the request of the department to place the property on the assessment list, or to correct the incorrect assessment or valuation, the department may prepare a supplement to the assessment list, which supplement shall include all property required by the department to be placed on the assessment list and all corrections required to be made. The supplement shall be filed with the assessor's assessment list and shall thereafter constitute an integral part thereof to the exclusion of all portions of the original assessment list inconsistent therewith.

(3) If the department ascertains that the work of a county assessor is not being carried out as provided by law, the department shall notify the governing body of that fact by written report. If applicable, the report shall contain recommendations for appointment of a special assessor as provided under ORS 308.055.