Oregon Revised Statutes Revenue and Taxation § 316.367

(1) No joint return shall be made under this chapter if the spouses are not permitted to file a joint federal income tax return;

(2) If the federal income tax liability of either spouse is determined on a separate federal return, their income tax liabilities under this chapter shall be determined on separate returns;

(3) If the federal income tax liabilities of the spouses are determined on a joint federal return, they shall file a joint return under this chapter and their tax liabilities shall be joint and several; and

(4) If neither spouse is required to file a federal income tax return and either or both are required to file an income tax return under this chapter, they may elect to file separate or joint returns and pursuant to such election their liabilities shall be separate or joint and several.