CSLB C-10 Licensing: What You Must Know for the Exam

1. The CSLB C-10 License

The Contractors State License Board (CSLB) issues the C-10 Electrical Contractor license, which authorizes the holder to install, construct, maintain, repair, and alter electrical wiring, apparatus, and equipment. To qualify for a C-10 license, applicants must have at least 4 years of journeyman-level experience within the last 10 years, pass a two-part exam (Law & Business and Trade), and pay the required fees.

The license application also requires a $25,000 contractor's bond filed with the CSLB, and proof of workers' compensation insurance if the contractor employs anyone other than themselves. C-10 licenses must be renewed every 2 years. If the license lapses for more than 5 years, the applicant must retake the exam. Any work performed under a suspended license is illegal — contracts entered during suspension are unenforceable, meaning the contractor cannot collect payment even if the work is done.

2. DIR Registration (Separate from CSLB)

The California Department of Industrial Relations (DIR) requires all electrical contractors working on public works projects to register with the DIR's Public Works Contractor Registration program. Registration costs $400 per year and must be renewed annually. Any contractor who fails to register — or who uses unregistered subcontractors on public works — faces penalties of up to $1,000 per day and may be subject to contract termination.

DIR registration is completely separate from your CSLB license. You can hold a valid C-10 and still be unregistered with DIR, which would make you ineligible to bid on public works. The DIR also enforces prevailing wage requirements — all workers on public works projects must be paid the prevailing wage for their specific trade and county. As a C-10 licensee, you are responsible for verifying that your subcontractors are also DIR-registered. The prime contractor bears the compliance burden — "I didn't know" is not a defense.

3. How the Exam Is Actually Structured

The CSLB C-10 exam is two separate tests administered on the same day. The Law & Business exam has approximately 115 questions and the Trade exam has approximately 120 questions — roughly 235 questions total. Each section is timed separately. You must pass each section with a minimum score of 70%. Passing one section does not carry over if you fail the other — you must retake both if you fail either one. Exams are closed-book and administered at PSI testing centers throughout California.

The Trade exam covers NEC code application, electrical theory, motor calculations, load calculations, overcurrent protection, grounding, wiring methods, and California-specific amendments. Approximately 25-30% of trade questions involve calculations — load calcs, motor sizing, conduit fill, and demand factors. The Law & Business exam covers contractor licensing, bonds, insurance, labor law, Cal/OSHA, contracts, and business practices. Both exams use scenario-based questions, not simple recall — you'll be applying concepts to realistic job-site situations.