RCW 41.32.035: Employer contribution rates—Computation and payment.

The amount paid by each employer shall be computed by applying the rates established under chapter 41.45 RCW to the total earnable compensation of the employer's members as shown on the current payrolls of the employer. The employer's contribution shall be paid at the end of each month in the amount due for that month, except as provided in RCW 41.32.013.