(1) When a provider of health services receives a payment to which that provider is not entitled, the provider must repay the excess payment, plus accrued interest, without regard to whether the excess payment occurred due to provider or department error or oversight, except as provided in subsection (2) of this section.

(2) When a provider:

(a) Accepts in good faith a determination by the department that a worker is eligible for benefits under Title 51 RCW;

(b) Provides, bills, and receives payment for services to that worker and the department later determines that the worker was ineligible for services during that period no interest will begin to accrue until notification is received by the provider that the worker was ineligible.

(3) Interest accrues on excess payments at the rate of one percent per month or portion of a month beginning on the thirty-first day after payment was made. Where partial repayment of an excess payment is made, interest accrues on the remaining balance.

(4) The department reserves the option of either requesting the provider to remit the amount of the excess payment and accrued interest to the department or offsetting excess payments and accrued interest against future payments due to the provider.