(1) The method of accounting of a partnership, REMIC (real estate mortgage investment conduit) or taxpayer shall be the same as the method of accounting which the partnership, REMIC or taxpayer uses for federal income tax purposes for the taxable year.
(2) Notwithstanding subsection (1) of this section, if the method of accounting used by the partnership, REMIC or taxpayer does not clearly reflect income, the computation of taxable income shall be made under such method as the Department of Revenue may prescribe.
(3) If the method of accounting is changed for federal income tax purposes, the partnership, REMIC or taxpayer shall adopt the same method of accounting for purposes of ORS chapter 316, 317 or 318 and shall use that method beginning with the return filed which corresponds to the first federal return filed which is required to use the new method. Any adjustments required to prevent amounts from being duplicated or omitted shall be taken into account for state tax purposes in the same manner as for federal tax purposes.
(4) Subsections (1) and (3) of this section shall not apply with respect to methods of accounting which are disallowed for purposes of ORS chapter 316, 317 or 318.