2015 ORS § 305.125¹
Application of administrative rules

The Department of Revenue may not apply an administrative rule in a manner that requires a change in the treatment of an item of income or expense, a deduction, exclusion, credit or other particular on a report or return filed by a taxpayer if:

(1) The taxpayer filed the report or return by the date it was due; and

(2) The treatment of the item on the report or return was consistent with an administrative rule adopted and in effect at the time that the report or return was filed. [2009 c.494 §2]