3.19.090 Underpayment of tax, interest, or penalty—Interest.
A. If, upon examination of any returns, or from other information obtained by the director, it appears that a tax or penalty less than that properly due has been paid, the director shall assess the additional amount found to be due and shall add thereto interest on the tax only. The director shall notify the person by mail of the additional amount, which shall become due and shall be paid within thirty days from the date of the notice, or within such time as the director may provide in writing.
B.
1. For tax liabilities arising after December 31, 1991, and until January 1, 2005, from the date of the liability to the date of payment, the rate of interest shall be variable and shall be an average of the federal short-term rate as defined in 26 U.S.C. Section 1274(d) plus two percentage points. The average will be computed as provided in RCW 82.32.050(2).
2. For tax periods after December 31, 2004, the director shall compute interest in accordance with RCW 82.32.050 as it now exists or as it may be amended.
3. If subsection (B)(2) of this section is held to be invalid, then the provisions of RCW 82.32.050 existing at the effective date of the ordinance codified in this section shall apply. (Ord. 3710-19 § 1, 2019.)