(1) All billable services provided under chapter 15.13 RCW are due and payable upon billing by the department. For the convenience of established accounts and in accord with good business practices, the department provides a monthly billing service for established accounts. Accounts not paid-in-full within thirty days of billing are considered delinquent.

(2) All delinquent accounts are assessed a late charge equal to one and one-half percent per month, or portion of a month, on the unpaid balance.

(3) Except for established accounts where there is a reasonable expectation of additional charges during a calendar month, the minimum billable amount through the monthly billing system is twenty dollars. All billable services of less than twenty dollars are due and payable-in-full at the time that service is rendered.

(4) No person with an account ninety days or more in arrears will receive service except on the basis of payment in full at the time service is rendered. Such accounts will not be restored to monthly billing status until all past due accounts are paid-in-full. Such accounts may be subject to legal action for collection.

(5) Accounts that become ninety days or more in arrears twice within a five-year period may be subject to a permanent requirement for payment in full at the time service is provided.