Workers' Comp Premium Audits in California: What to Expect, How to Prepare, How to Dispute
A workers' comp premium audit is how your insurer turns the estimated premium you paid at the start of the year into the actual premium you owe. After the policy ends, the insurer compares the payroll you estimated with the payroll you actually paid, checks the class codes, and bills you for the difference (or refunds it). A large audit bill almost always comes from one of three things: payroll that grew without anyone telling the insurer, workers assigned to the wrong class, or 1099 payments the auditor treated as payroll.
This guide covers why audits happen, what auditors ask for, what counts as payroll in California, the overtime and subcontractor rules, how to dispute a result, and how to prepare. For how the base premium is built, see how workers' comp premiums are calculated. If you'd like a second set of eyes on your program, start with our business insurance page.
Why audits happen
Workers' comp is priced on payroll, which nobody knows in advance:
At the start of the policy, you pay a deposit premium based on estimated payroll by class code.
After the policy expires, the insurer audits actual payroll and classifications.
You get an audit statement showing additional premium owed or a return premium.
Your insurer reports the audited payroll and claims to the WCIRB, where they feed your future experience modification. The WCIRB also spot-checks insurers' audits with about 3,000 random test audits a year.
Physical vs. voluntary audits
California's audit rules are in the Uniform Statistical Reporting Plan (USRP), Part 3, Section VI, Rule 4. For policies effective on or after September 1, 2026:
Your policy | Audit required |
Final premium $10,500 or more | Physical audit at least once a year, and the last audit must be a physical audit of the full policy period |
Final premium under $10,500 | Physical audits "at sufficient intervals"; otherwise a voluntary audit (a signed payroll statement) |
Under $10,500 with payroll in a dual wage construction class | Physical audit, unless it's a renewal and one of the two prior policy periods was physically audited |
C-39 roofing licensee | Physical audit of the complete policy period every year, plus an annual in-person visit to verify employee count (Ins. Code §11665) |
A physical audit can be done remotely. The WCIRB says what matters is that the auditor examines your original payroll records, which can be provided electronically.
What auditors typically ask for
Requests vary, but expect most of these:
Payroll registers or journals for the full policy period, by employee
Quarterly payroll tax filings: federal Form 941 and California DE 9 / DE 9C
Year-end W-2 and W-3 summaries
General ledger or cash disbursement records, so the auditor can find payments that never went through payroll (such as subcontractors, casual labor or cash)
Form 1099 records and a list of all subcontractors or independent contractors paid
Certificates of insurance for every subcontractor
Job descriptions and an explanation of what each employee actually does
Time cards that show hours by type of work, if any employee's payroll is split between classes
Officer, partner or member information, including any signed exclusion forms
Don't ignore the audit. According to the WCIRB, if an insurer can't complete an audit, the payroll is reported as "estimated." The Experience Rating Plan doesn't allow unaudited payroll in an experience mod. Your claims still count but that year's payroll doesn't, which typically drives the mod up. Check your policy's audit provisions, too. Policies typically let the insurer bill premium on estimated figures when you don't cooperate.
What counts as payroll in California
Workers' comp payroll isn't the same as IRS taxable wages. Apart from specific exceptions in USRP Part 3, Section V, Rule 1, the WCIRB says all money and substitutes for money earned by covered employees and officers during the policy period is payroll.
Usually included | Usually excluded |
Gross wages and salaries | Premium portion of overtime (if your records separate it, see below) |
Commissions and all bonuses | Tips |
Vacation, holiday and sick pay | Meals or lodging (unless the class wording includes them or they're given in place of wages) |
Most profit sharing | Severance pay (except accrued vacation, sick pay, commissions and bonuses) |
Market value of gifts | Employer contributions to qualified insurance, stock or retirement plans |
Auto allowances, less documented expense reimbursements | Value of a company car furnished to an employee |
Straight-time portion of overtime | Uniform allowances; employee merchandise discounts |
Source: WCIRB, Payroll or Remuneration and Types of Compensation Included as Payroll/Remuneration. The USRP's Appendix II has the full table.
Owners and officers
When executive officers, partners, individual employers and LLC members are covered, their payroll is reported within a minimum and maximum: $66,300 and $171,600 per person for policies effective on or after September 1, 2026 (WCIRB). If an owner has validly elected out of coverage under Labor Code §3352, keep the signed exclusion on hand for the auditor.
The overtime rule: keep the records or pay on all of it
Only the straight-time portion of overtime is payroll. The premium portion, meaning the extra half in time-and-a-half, can be excluded, but only if your records allow it. Under USRP Part 3, Section V, Rule 1c, as summarized by the WCIRB, the premium portion is excluded only when you keep records that show, separately by employee and in summary by type of operation, either:
pay at regular rates for all hours worked and the premium portion of overtime, or
pay at regular rates for non-overtime hours and total pay for overtime hours.
(The exclusion doesn't apply to operators of athletic teams.)
Example: 10 overtime hours at $45 for a $30-an-hour employee is $450. With qualifying records, only the $300 of straight time is payroll. Without them, all $450 may be counted. Ask your payroll provider for an overtime premium report before the audit.
Subcontractors without certificates can become your payroll
This is the biggest audit surprise for contractors, trucking companies and many service businesses.
California law presumes that people who work for you are employees. Labor Code §3357 says anyone rendering service for another, other than as an independent contractor, is presumed to be an employee. Under Labor Code §3351(i), workers who are employees under the ABC test in §2775 are employees for workers' comp. And under Labor Code §2750.5, a worker doing work that requires a contractor's license is presumed to be an employee. Holding a valid license is a condition of independent-contractor status.
Insurers apply these rules at audit. The State Compensation Insurance Fund, for example, says that payments to uninsured and/or unlicensed workers reported on Form 1099 "may be subject to premium and may be included in the audit as payroll," decided case by case. For construction classes, it says that if you can't produce a certificate of insurance for a subcontractor at audit and the subcontractor has no valid license, it may treat the sub as an employee and charge the appropriate premium.
What that means in practice:
Collect a certificate of workers' comp insurance from every sub who has employees, before they start. Use our certificate of insurance request template and our guide on how to read a certificate of insurance.
Check the CSLB license of every construction sub and keep a dated printout. Our contractor insurance verification checklist walks through it.
Keep the written contract and invoices for each sub, so the auditor can see a business-to-business relationship.
For the classification rules behind all of this, see 1099 contractors and workers' comp. Contractors should also note that the CSLB requirement expands in 2028. See our guide to the SB 216 contractor requirement.
Facing a large audit bill or a reclassification? TSM is an independent agency — we compare carriers for you. Call (209) 524-6366 (Modesto) or (530) 221-3031 (Redding).
Class codes at audit: records decide
Auditors check what each employee actually did. Two USRP rules matter most:
Dividing one employee's payroll. You can split an employee between classes only with contemporaneous records (original time cards or time book entries) that show the split by employee and are totaled by operation. If you don't have them, the entire payroll goes to the highest-rated class that applies to any part of the employee's work. Percentages and estimates aren't allowed. No particular format is required, and the WCIRB has confirmed that an auditor can't insist on a spreadsheet.
Dual wage construction classes. To use the lower-rated, higher-wage code, you need time cards showing the operations performed, total daily hours and start and stop times for each work period, or a valid collective bargaining agreement with a matching roster. If you can't show those, the payroll goes to the higher-rated code.
If an insurer changes your classification in a way that raises your premium, it must notify you in writing of the change and the reasons, and tell you about your right to request reconsideration and appeal (Ins. Code §11753.1(b)).
How to dispute an audit in California
Start informally. Most audit errors are fixed with a phone call and the right document. Your agent should request the auditor's worksheets so you can see exactly what was counted. If that doesn't work, California has two formal tracks, depending on who made the decision.
Track 1: The insurer's decision (most audit disputes)
Audit payroll, the classification of your employees, employment status, how your mod was applied and premium billing are all insurer issues.
Make a written request to the insurer. Insurance Code §11737(f) requires every insurer to provide a way for any person aggrieved by how its rating system was applied to be heard on written request. The WCIRB says the dispute must be in writing and sent to the insurer's designated office. The contact details are in the policyholder notice attached to your policy, "Your Right to Rating and Dividend Information," under "Our Dispute Resolution Process."
The 30-day clock. If the insurer doesn't grant or reject your request within 30 days, you can proceed as if it had been rejected.
Appeal to the Insurance Commissioner within 30 days after written notice of the insurer's action (§11737(f)). Appeals go to the Administrative Hearing Bureau of the California Department of Insurance. A hearing is generally held within 60 days of the appeal request, though the Commissioner can deny an appeal without a hearing if there's no reasonable basis for it or it isn't made in good faith.
Track 2: The WCIRB's decision
Classification findings on a WCIRB inspection report and the calculation of your experience mod are WCIRB issues.
Request reconsideration from the WCIRB under Insurance Code §11753.1(a), following the procedures in the USRP and Experience Rating Plan ("Inquiries, Complaints and Requests for Action, Reconsideration, and Appeals").
If the WCIRB rejects the request or doesn't act within 30 days, you can appeal to the Commissioner by filing a written complaint and request for hearing.
The WCIRB's Policyholder Ombudsman can answer questions about payroll and classification rules, but isn't a step in the formal appeal process.
Pay what isn't in dispute. Unpaid premium is typically grounds for cancellation under most policies. For contractors, the law has an extra risk: if an insurer completes an audit, finds a material misrepresentation that caused it financial harm and isn't reimbursed, it must report the licensee to the CSLB (Bus. & Prof. Code §7125(e)).
How to prepare: a checklist
During the policy year
☐ Tell your agent when payroll, headcount or operations change significantly, so your deposit tracks reality
☐ Collect sub certificates and check licenses before work starts, and diary certificate expiration dates
☐ Keep time cards by operation for split employees, with start and stop times for dual wage construction classes
☐ Set up payroll to report the premium portion of overtime separately
☐ Keep signed officer or owner exclusion forms on file
Before the auditor arrives
☐ Pull 941s, DE 9/DE 9Cs, the payroll register, the general ledger and the 1099 list for the exact policy period (it may not match the calendar year)
☐ Match every 1099 payee to a certificate or a license printout
☐ Write a one-page description of what each job title actually does
☐ Ask your agent to review the preliminary audit before it's finalized
After: compare the audit to your records, dispute in writing on time, and use the audited payroll to set next year's deposit. Review it at renewal with our annual insurance review checklist, and if service has broken down, see switching workers' comp carriers.
FAQs
Why did I get a workers' comp audit bill?
Your actual payroll was higher than estimated, some payroll was assigned to a higher-rated class, or the auditor counted payments to uninsured or unlicensed workers as payroll. The audit sets your final premium.
Is overtime included in workers' comp payroll in California?
The straight-time portion is. The premium portion (the extra above the regular rate) is excluded only if your records show it separately by employee and in summary by operation (USRP Part 3, Section V, Rule 1c).
Do I have to pay workers' comp premium on 1099 subcontractors?
Possibly. Payments to uninsured or unlicensed workers may be included as payroll at audit. For construction, an unlicensed sub without a certificate is likely to be charged (Labor Code §2750.5). Collect certificates and verify licenses.
What happens if I don't complete my workers' comp audit?
Policies typically let the insurer bill on estimated figures, and the WCIRB won't use unaudited payroll in your experience mod. Your claims still count but the payroll doesn't, which typically raises the mod.
How do I dispute a workers' comp audit in California?
Send the insurer a written request for review under its dispute process (Ins. Code §11737(f)). If it rejects the request or doesn't respond within 30 days, you can appeal to the Insurance Commissioner within 30 days of its written action. Mod calculations and WCIRB inspection findings go to the WCIRB first (§11753.1).
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