Every public service company subject to regulation by the commission shall, on or before the date specified by the commission for filing annual reports under RCW 80.04.080, file with the commission a statement on oath showing its gross operating revenue from intrastate operations for the preceding calendar year or portion thereof and pay to the commission a fee equal to one-tenth of one percent of the first fifty thousand dollars of gross operating revenue, plus ((two-tenths))four-tenths of one percent of any gross operating revenue in excess of fifty thousand dollars: PROVIDED, That the commission may, by rule, set minimum fees that do not exceed the cost of collecting the fees. The commission may by rule waive any or all of the minimum fee established pursuant to this section.

The percentage rates of gross operating revenue to be paid in any year may be decreased by the commission for any class of companies subject to the payment of such fees, by general order entered before March 1st of such year, and for such purpose such companies shall be classified as follows:

Electrical, gas, water, telecommunications, and irrigation companies shall constitute class one. Every other company subject to regulation by the commission, for which regulatory fees are not otherwise fixed by law shall pay fees as herein provided and shall constitute additional classes according to kinds of businesses engaged in.

Any payment of the fee imposed by this section made after its due date shall include a late fee of two percent of the amount due. Delinquent fees shall accrue interest at the rate of one percent per month.