Oregon Revised Statutes Revenue and Taxation § 309.200

(1) Between January 1 and December 31 of each year the county assessor shall collect sales data for a ratio study.

(2) The assessor shall prepare and complete a certified ratio study in the time and manner provided by the rules adopted by the Department of Revenue. A copy of the sales data collected and used as the basis for conclusions relating to real market value shall be included with the ratio study. The assessor shall file a certified copy of the sales data and ratio study with the department, as prescribed by department rule.

(3) Not later than October 15 of each year the assessor shall file with the clerk of the board of property tax appeals a copy of the ratio study.