Oregon Revised Statutes Revenue and Taxation § 314.732

(2)(a) Subject to paragraphs (b) to (d) of this subsection, the taxable income of an S corporation shall be computed pursuant to section 1363(b) of the Internal Revenue Code,  1 with the modifications, additions and subtractions provided in this chapter and ORS chapter 316.

(b) Except as otherwise provided under this chapter and ORS chapter 316, 317 or 318, and except as inconsistent with ORS 314.730 to 314.752, subchapter C, chapter 1, Internal Revenue Code, shall apply to an S corporation and its shareholders for Oregon tax purposes. For Oregon tax purposes, the provisions of section 1371 of the Internal Revenue Code shall apply, subject to the modifications, additions and subtractions under this chapter or ORS chapter 316, 317 or 318 and any provisions to the contrary in this chapter or ORS chapter 316, 317 or 318.

(c) Notwithstanding ORS 317.476, 317.478 or 317.479, no carryforward, arising for a taxable year for which a corporation is a C corporation, may be carried to a taxable year for which such corporation is an S corporation.

(d) Notwithstanding ORS 317.476 or other law, no carryforward, and no carryback, shall arise at the corporate level for a taxable year for which a corporation is an S corporation.