Washington Revised Code Title 35. Cities and Towns § 35.49.030. Ordinance to prescribe time of payment--Interest--Penalties

Every city and town shall prescribe by ordinance within what time assessments or installments thereof shall be paid, and shall provide for the payment and collection of interest thereon at a rate as shall be fixed by the legislative body of the city or town. Assessments or installments thereof, when delinquent, in addition to such interest, shall bear such penalty not less than five percent as shall be by general ordinance prescribed.