Oregon Revised Statutes Revenue and Taxation § 319.820

(1) If the Department of Transportation determines any amount of tax or penalty has been paid more than once or has been erroneously or illegally collected, the department shall credit such amount against any amounts then due from the user or seller under ORS 319.510 to 319.880 or 319.990 (4) and shall refund any balance to the user or seller, the successor, administrator or executor of the user or seller.

(2) A user or seller may claim a credit or refund for any amount of tax or penalty which the user or seller has paid more than once or which the user or seller has paid or which has been collected erroneously or illegally. No such claim for a credit or refund shall be allowed unless the claim is filed with the department within three years from the date of the payment or collection or, with respect to an assessment made under ORS 319.760 and 319.780, within six months after the assessment becomes conclusive, whichever period expires the later. Every such claim must be in writing and must state the specific grounds upon which it is founded. Failure to file such claim within the time prescribed in this section shall constitute waiver of any and all demands against this state on account of overpayments under ORS 319.510 to 319.880. Within 30 days of allowing or disallowing any such claim in whole or in part, the department shall serve notice of such action on the claimant. The service shall be made in the manner prescribed by ORS 319.760 (3).