An employer that has not been in business in Washington long enough to report four calendar quarters by September 30th will have its size calculated after the second quarter of reporting is due by averaging the number of employees reported over the quarters for which reporting exists. Premium assessment based on this determination will begin on this reporting date. This size determination remains in effect for the following calendar year under RCW 50A.10.030.
Wash. Admin. Code § 192-510-050