Does a California plumbing contractor have to carry workers' compensation insurance?

Yes, if you have even one employee. California law requires every employer with one or more employees to carry workers' compensation insurance (Labor Code §3700). That applies the day you hire your first apprentice, helper or office person, whether they are full-time, part-time or seasonal, and whether your company is a sole proprietorship, partnership, corporation or LLC.

If you are a C-36 licensee with no employees at all, the law does not currently require a policy. You can keep your license active by filing a workers' compensation exemption with CSLB certifying that you have no employees. Two cautions: the exemption is not available if your license is qualified by a responsible managing employee (RME), and it becomes invalid the moment you hire someone subject to California workers' compensation law. CSLB must receive proof of coverage within 90 days of that hire.

The exemption also has an end date. Under SB 216, as amended by SB 1455, every licensed contractor will be required to carry workers' compensation whether or not they have employees starting January 1, 2028. Five classifications (C-8, C-20, C-22, C-39 and C-61/D-49) have already been under that rule since 2023; C-36 is not one of them yet.

Separately from the law, general contractors, property managers and public owners routinely require a certificate of workers' compensation before you can work on their jobs, even from a one-person shop. In practice, most working plumbers end up needing a policy for contract reasons before the 2028 deadline reaches them.