(1) Except as provided in subsection (4) of this section, vendors shall pay interest on overpayments at the rate of one percent per month or portion thereof. Where partial repayment of an overpayment is made, interest accrues on the remaining balance. Interest will not accrue when the overpayment occurred due to department error.

(2) If the overpayment is discovered by the vendor prior to discovery and notice by the department, the interest shall begin accruing ninety days after the vendor notifies the department of such overpayment.

(3) If the overpayment is discovered by the department prior to discovery and notice by the vendor, the interest shall begin accruing thirty days after the date of notice by the department to the vendor.

(4) This section does not apply to:

(a) Interagency or intergovernmental transactions;

(b) Contracts for public works, goods and services procured for the exclusive use of the department, equipment, or travel; and

(c) Contracts entered into before September 1, 1979, for contracts with medical assistance funding, and August 23, 1983, for all other contracts.

Severability—Savings—1987 c 283: See notes following RCW 43.20A.020.

Savings—1983 1st ex.s. c 41 s 17: "The enactment of section 17 of this act shall not have the effect of terminating or in any way modifying any liability, civil or criminal, which is already in existence on August 23, 1983." [ 1983 1st ex.s. c 41 s 18.]

Severability—1983 1st ex.s. c 41: See note following RCW 26.09.060.