Oregon Revised Statutes Revenue and Taxation § 305.625

If the ordinances of any city or county in this state provide for the collection of an income tax, in whole or in part, by imposing on employers generally the duty of withholding sums from the compensation of individuals employed within the boundaries of the city or county and making returns of such sums to the authorities of such cities or counties, then the State of Oregon or any political subdivision is considered to be an employer as to its employees who come within the jurisdictional limits of the ordinance of the city or county.