(1) Unless specifically provided otherwise by statute or by rule of the Director of the Department of Revenue adopted pursuant to subsection (3) of this section, every deficiency or delinquency arising under any law administered by the Department of Revenue shall bear simple interest at the rate of five-sixths of one percent per month or fraction thereof.
(2) Unless specifically provided otherwise by statute or by rule of the director adopted pursuant to subsection (3) of this section, every refund arising under any law administered by the department shall, subject to subsections (3) and (5) of this section and ORS 305.222 (Determination of interest rate), bear simple interest at the rate of five-sixths of one percent per month, or fraction thereof.
(3)(a) If the director determines that the rates of interest for deficiencies, delinquencies and refunds established in subsections (1) and (2) of this section are at least one percentage point more or less than the prevailing rates of interest established by the Internal Revenue Service for underpayments arising under the federal tax laws to which one percentage point has been added, the director may adopt, by rule, adjusted interest rates. The director shall not adopt adjusted interest rates more than once in a calendar year. Notice of intent to adopt adjusted interest rates shall be given in the manner provided in ORS 183.335 (Notice), not less than three months before the proposed effective date of the adjusted rates.
(b) In establishing the adjusted interest rates to be adopted under this subsection:
(A) The director shall take into consideration the current interest rates established by the Internal Revenue Service for underpayments arising under the federal tax laws.
(B) To any interest amount determined by taking into consideration the current interest rates established by the Internal Revenue Service for underpayments under subparagraph (A) of this paragraph, which interest amount shall be expressed at a rate per month or fraction thereof, there shall be added one-twelfth of one percent.
(4) If the director adopts an adjusted interest rate for deficiencies and delinquencies, the director shall adopt an adjusted interest rate for refunds that is equal to the adjusted interest rate for deficiencies and delinquencies.
(5) Any change in the rate of interest applicable to deficiencies, delinquencies or refunds resulting from the adoption of adjusted interest rates by the director under this section shall apply to deficiencies, delinquencies and refunds outstanding on the effective date of the rule, or arising on or after that date, but only with respect to interest periods beginning on or after that date.
(6) If the rate of interest on a deficiency, a delinquency or a refund is governed by this section, and if a fraction of a month is involved in making the computation of interest on the deficiency, delinquency or refund, then for the fractional month, the simple interest otherwise provided shall be computed on a daily basis. [1982 s.s.1 c.16 §2; 1987 c.647 §5; 2001 c.114 §§2,4]