| Note: This is probably a standard in Amercia |
In Washington state, where an employer insured with the state fails or refuses to file any report of payroll required by the department and fails or refuses to pay the premiums due on such unreported payroll, the department shall have authority to estimate such payroll and the premiums due thereon and collect premiums on the basis of such estimate.
If the report required and the premiums due thereon are not made within ten days from the mailing of such demand by the department, which shall include the amount of premiums estimated by the department, the employer shall be in default as provided by this title and the department may have and recover judgment, warrant, or file liens for such estimated premium or the actual premium, whichever is greater.
The director or the director’s designee may compromise the amount of premiums estimated by the department, whether reduced to judgment or otherwise, arising under this title if collection of the premiums estimated by the department would be against equity and good conscience.
RCW 51.16.155
Small Independent Business Reporting 
my employer is paying the tax but charging me DOUBLE the legal amount and refuses to refund it
send an anonymous letter to the State for in audit. Never admit you did so.
Your State may have you pay a portion of the Workers Comp per statute.
Good luck.