Workers' Compensation Insurance for California Plumbing Companies

The short version

Workers' compensation is the one insurance policy California tells a plumbing company it must buy, and it is usually the largest premium that company pays. The law is short: an employer with one or more employees must carry it. The policy does two jobs. Part One pays statutory benefits to an employee hurt on the job, no matter who was at fault. Part Two, employers' liability, defends and pays on behalf of the company when a work injury turns into a lawsuit the benefit system does not resolve.

The premium is not a flat fee. It is calculated from the payroll you pay in each workers' compensation classification, multiplied by a rate for that classification, multiplied again by your experience modification once your company is large enough to have one. Because the premium is based on payroll, the number you pay at the start of the year is an estimate, and the real bill is settled at an audit after the year ends.

A realistic scenario

A service plumber in Fresno has run a one-man C-36 for six years with a workers' compensation exemption on file at CSLB. In March he hires his first employee, a helper who rides along, pulls water heaters and runs the drain machine. In June he adds a second helper. He plans to sort out the insurance at his license renewal in the fall.

In July the second helper is stripping a galvanized nipple with a torch and takes a serious burn to his forearm: urgent care, a burn clinic, five weeks off work. There is no workers' compensation policy to bill.

Under California law the owner is now an illegally uninsured employer, and the injured helper's benefits are ultimately his to pay. The state's Uninsured Employers Benefits Trust Fund may pay benefits to the injured worker, but it then pursues reimbursement from the employer through every available avenue, including liens against the employer's property. He also faces the penalties the Department of Industrial Relations lists for operating uninsured: a misdemeanor charge carrying a fine of not less than $10,000 and up to a year in county jail, a stop order that bars him from using employee labor until he has a policy, and a civil penalty of the greater of twice the premium he should have paid or $1,500 per employee. If the claim reaches the Workers' Compensation Appeals Board, the uninsured-employer penalty is $10,000 per payroll employee for a compensable injury, up to $100,000. CSLB suspends his license, and the jobs he completed while suspended are treated as unlicensed work.

His exemption became invalid the day the first helper started in March. CSLB should have had proof of coverage within 90 days of that hire.

Who must carry it

One employee is the trigger

California Labor Code section 3700 requires every employer with one or more employees to carry workers' compensation insurance or qualify as a self-insurer. The Department of Industrial Relations states the rule in one sentence: if a business employs one or more employees, it must satisfy the requirement of the law. Part-time, temporary, seasonal and probationary workers are all employees. So are family members on payroll. So, often, are the people a plumbing company calls independent contractors but pays by the hour, schedules, supervises and equips; a 1099 does not control how the state classifies them.

The CSLB exemption and when it ends

CSLB enforces the requirement at the license level. Every active licensee must have either a policy or an exemption on file. A C-36 licensee with no employees may file an exemption certifying that fact, unless the license is qualified by a responsible managing employee or holds one of the classifications that must carry coverage regardless of employees (C-8, C-20, C-22, C-39 and C-61/D-49). Plumbing is not on that list today.

The exemption becomes invalid the moment the contractor hires an employee subject to California workers' compensation law, and CSLB must receive proof of coverage within 90 days of the hire. Failure to maintain required coverage results in license suspension, and work performed while suspended is treated as unlicensed. Our C-36 license guide covers the CSLB side in more detail.

January 1, 2028

Senate Bill 216 originally required all licensed contractors, with or without employees, to carry workers' compensation by January 1, 2026. Senate Bill 1455, signed in 2024, postponed that universal requirement to January 1, 2028. A sole operator planning to stay exempt should plan around that date, and check CSLB's workers' compensation page before relying on it, because legislative dates can move. If you plan to hire before then, the requirement arrives the day you hire; see Insurance considerations when hiring your first plumbing employee.

What the policy pays

Part One: the benefits

A California workers' compensation policy pays the benefits the Labor Code requires for an employee injured in the course of employment, without regard to fault. In general terms those benefits fall into five groups:

• Medical treatment for the injury, including surgery, physical therapy, prescriptions and follow-up care, generally directed through a medical provider network (MPN) when the employer or its insurer has an approved one, with limited exceptions such as an employee who properly predesignated a personal physician before the injury.
• Temporary disability, a wage-replacement payment while the employee is unable to work during recovery. It is generally two-thirds of the employee's average weekly wage, subject to a minimum and maximum weekly rate that the Division of Workers' Compensation publishes by date of injury and that changes each year.
• Permanent disability, weekly payments for any lasting impairment once the employee has recovered as far as medicine expects. The impairment is converted to a percentage under the state's Permanent Disability Rating Schedule, which also adjusts for occupation and age, and the weekly rate is subject to limits set by date of injury.
• Supplemental job displacement benefit, a non-transferable voucher for retraining or skill enhancement. For injuries on or after January 1, 2013 it is a flat $6,000, available when the injury causes permanent partial disability and the employer does not offer regular, modified or alternative work within 60 days after the claims administrator receives a medical report saying so.
• Death benefits to dependents, in amounts set by statute that depend on the number of total and partial dependents, plus burial expenses, when an injury is fatal.

In exchange for benefits paid regardless of fault, an employee generally cannot sue the employer in civil court over a covered injury. The Department of Industrial Relations puts the condition plainly: workers' compensation is the exclusive remedy for on-the-job injuries only when the employer is properly insured. An uninsured employer can be sued civilly on top of the workers' compensation claim.

Part Two: employers' liability

Not every work-injury claim stays inside the benefit system, which is why the policy has a second part. Employers' liability coverage responds when a work injury produces a lawsuit against the employer that the benefit system does not absorb, subject to its limits and exclusions, and it is the coverage a GC is checking when the subcontract specifies employers' liability limits on the certificate of insurance. One boundary matters for plumbing subcontractors. In the common third-party-over situation, your plumber is hurt on a general contractor's site, sues the GC, and the GC demands that you indemnify it under the subcontract. The standard employers' liability form generally excludes liability you assumed under a contract, so a demand that rests on the subcontract's indemnity clause is usually a question for your general liability policy's contractual liability coverage instead. In California, Labor Code section 3864 generally bars a third party from recovering from the employer at all unless the employer agreed in writing, before the injury, to indemnify it. Limits vary by insurer and policy, so compare the limits on the quote with the highest limit any of your contracts requires. General liability vs. workers' compensation for plumbers explains where this coverage ends and general liability begins.

How the premium is built

Estimated premium = (payroll per classification ÷ 100) × classification rate × experience modification, plus or minus the insurer's adjustments

Payroll. Premium is charged per $100 of remuneration, by employee, by classification. Under WCIRB's rules remuneration includes wages, the straight-time portion of overtime, all bonuses, and vacation, holiday and sick pay; it excludes the overtime excess (the increase above the regular hourly wage), tips, severance pay (except accrued vacation, sick pay, commissions and bonuses) and, in most classifications, meals and lodging. Payments to a subcontractor who cannot produce a certificate of workers' compensation insurance are typically added to your payroll at audit.

Classification. In California, plumbing payroll is assigned to the dual-wage pair 5183 and 5187 by each employee's regular hourly wage against a threshold set by WCIRB: $32 an hour for policies effective on or after September 1, 2024 (unchanged for September 1, 2025), and $35 an hour for policies effective on or after September 1, 2026, under the rating rules the Insurance Commissioner approved for that date. Employees paid at or above the threshold go in 5187, the lower-rated code; employees below it go in 5183, the higher-rated one; and payroll whose hourly wage cannot be verified from original time records is assigned to 5183 at audit. Clerical staff who never touch the field belong in 8810, and outside salespeople in 8742, each at a much lower rate. Workers' compensation payroll classifications for plumbing contractors covers the rules.

Rate. Each insurer files its own rate per $100 of payroll for each classification with the California Department of Insurance, which is the part of the formula that shopping affects. WCIRB proposes advisory pure premium rates each year for the Insurance Commissioner's approval; they reflect expected loss costs, not an insurer's expenses, and insurers generally build their own filed rates from them or from their own data.

Experience modification. Once a company's expected losses over the three-year experience period reach WCIRB's eligibility threshold, WCIRB publishes an experience modification that multiplies the premium. A mod of 1.00 is average; 1.20 raises the manual premium 20 percent, 0.85 lowers it 15 percent. What is an X-Mod? explains how it is calculated.

Insurer adjustments. On top of the modified premium, the insurer may apply a schedule credit or debit based on its view of your operations and safety program, and adds the state assessments and surcharges calculated each year on insured employers' premium, such as the Uninsured Employers Fund and Subsequent Injuries Fund assessments and the fraud surcharge.

State Fund and the private market

California plumbing companies buy workers' compensation from two kinds of sources. The State Compensation Insurance Fund is, in the Department of Industrial Relations' words, a state-operated entity that transacts workers' compensation insurance on a non-profit basis, and it operates as the insurer of last resort when private insurers will not offer coverage. Private insurers write the rest of the market and compete on rate, schedule credits, service and the industries they prefer.

In general terms, a company's options widen as its history lengthens. A new plumbing company with no prior coverage, a high X-Mod or a lapse may find fewer private insurers willing to quote, and a broker will often include State Fund in the comparison. A company with several years of clean loss history and organized payroll records typically has more choices. No insurer's willingness to write a given account can be promised in advance; the comparison is done quote by quote. What does not change between sources is the law: Part One benefits are set by statute, so an injured plumber receives the same benefits regardless of who issued the policy.

The audit

Because premium is charged on payroll, the policy begins with an estimate and ends with an audit. After the policy expires, the insurer reviews your actual payroll by classification, usually from quarterly payroll tax filings, earnings records, overtime records, job descriptions and subcontractor certificates. The audited payroll replaces the estimate, and the difference is billed or returned.

The three audit outcomes that most often surprise plumbing contractors are payroll that grew faster than projected, dual-wage payroll moved to the higher-rated code because hourly records were missing, and subcontractor payments added to payroll because no certificate was on file. All three are preventable with records kept during the year. How to prepare for a workers' compensation premium audit is the checklist.

Practical takeaway

Buy the policy before the first employee starts, not after. The requirement is triggered by the hire, the exemption dies the same day, and the penalties for the gap are severe out of proportion to the premium.

Once you have the policy, treat it as a payroll system with an insurance policy attached. Keep hourly wage and time records that support the dual-wage split. Separate office payroll from field payroll in your books. Collect certificates from subcontractors before they start. Know your X-Mod and which years are in it. Put a modified-duty plan on paper so an injured plumber returns to work quickly, because lost time drives both the claim and the next three years of mods.

The Fresno plumber in our scenario needed a policy bound in March and a certificate sent to CSLB. The cost of that policy would have been a line item; the cost of its absence was his license, a penalty schedule and an injured employee's benefits paid from his own account.

When you are ready to price coverage for your crew, the quote page collects the payroll, classification and history information a producer needs to put real numbers in front of you.