Oregon Revised Statutes Revenue and Taxation § 323.325

No refund or credit for amounts overpaid for the purchase of stamps shall be allowed or approved after three years from the due date for payment of the purchase for which the overpayment was made, or with respect to a determination made pursuant to ORS 323.005 to 323.482, after six months from the date the determination becomes final, or after six months from the date of overpayment, whichever period expires the later, unless a claim therefor is filed with the Department of Revenue within the applicable period.