The entire year’s tax is due on or before April 30th. You may choose to pay half by April 30th and half by October 31st (if applicable). Interest and penalty will be charged on the entire principal balance. Real and Personal Property taxes less than $50.00 are due in full by April 30th. By Washington State law, the postmark is considered the received date for interest calculations. (RCW 1.12.070)