Every California employer with a workers’ compensation policy will go through a premium audit at the end of each policy period. The audit reconciles what you estimated at the start of the year with what actually happened: your real payroll, your actual headcount, and how your employees were classified. If your payroll grew, you’ll owe additional premium. If it shrank, you may get a refund.
Most audit surprises are avoidable. This guide walks through what the auditor is looking for, which records to have ready, and the mistakes that cost employers the most money.
Key Takeaways
- A workers’ comp premium audit compares your estimated payroll (used to set your initial premium) against your actual payroll for the policy period.
- If actual payroll exceeded the estimate, you will owe additional premium. If it was lower, you may receive a credit or refund.
- The auditor reviews payroll records, tax filings, class code assignments, overtime records, and subcontractor certificates of insurance.
- Misclassified employees, uninsured subcontractors, and poor overtime records are the three most common reasons employers overpay at audit.
- Keeping clean, audit-ready records throughout the year is the single best way to avoid surprises.
Contents
What Is a Workers’ Comp Premium Audit?
A workers’ compensation premium audit is a review conducted by your insurance carrier (or a third-party auditor) at the end of each policy period. Its purpose is to verify that the payroll figures and employee classifications used to calculate your premium were accurate.
When you buy a workers’ comp policy, you provide an estimate of your annual payroll broken down by class code. The carrier uses those estimates to calculate your deposit premium. At the end of the year, the audit compares your estimates to reality.
The result is an adjusted final premium. You either owe the difference (if payroll was higher than estimated) or receive a credit toward your next policy (if payroll was lower).
Why Audits Happen
Premium audits are a standard part of every workers’ compensation policy, not a sign that something is wrong. California law and WCIRB rules require carriers to audit policies to ensure premiums reflect actual exposure.
Audits serve three purposes:
- Fair pricing. You pay based on your actual payroll and risk, not a guess from 12 months ago.
- Accurate experience rating. Your EMR is based on expected losses, which are derived from payroll. Wrong payroll means a wrong EMR.
- Regulatory compliance. The WCIRB requires accurate classification and payroll data to maintain the integrity of California’s rating system.
Types of Audits
The type of audit you receive depends on your premium size, the complexity of your operations, and your carrier’s requirements.
| Audit Type | How It Works | When It’s Used |
|---|---|---|
| Physical audit | An auditor visits your office or job site and reviews original records in person. | Larger policies, complex operations, multiple class codes, or previous audit issues. |
| Voluntary / mail audit | Your carrier sends a form. You fill in payroll figures and mail or upload it with supporting documents. | Smaller policies with straightforward operations. |
| Phone / virtual audit | An auditor calls or video-conferences to walk through your records. | Mid-size policies or when an in-person visit isn’t practical. |
| Test audit | The WCIRB independently audits a sample of policies to verify carrier accuracy. | Random selection by the WCIRB, not triggered by the employer. |
Documents You Need to Have Ready
The best time to start preparing for your audit is the day your policy starts. Keep an audit folder (physical or digital) and add documents throughout the year. When the auditor calls, you’ll be ready.
Here is what they will ask for:
| Document | Why the Auditor Needs It |
|---|---|
| Quarterly payroll reports (by employee) | Verify total gross wages for each worker during the policy period |
| IRS Form 941 (quarterly) or Form 944 (annual) | Cross-check reported wages against payroll records |
| State unemployment (DE 9 / DE 9C in California) | Confirm payroll by employee and verify state of employment |
| Overtime records | Calculate the overtime exclusion (see payroll rules below) |
| Job descriptions for each role | Verify that each employee is assigned to the correct class code |
| Certificates of Insurance (COIs) for subcontractors | Confirm subs carry their own workers’ comp coverage |
| 1099 forms for independent contractors | Identify payments that may need to be added to auditable payroll |
| Officer/owner inclusion or exclusion waivers | Confirm whether corporate officers are covered or exempt |
What Counts as Auditable Payroll
Not every dollar you pay an employee counts toward your workers’ comp premium. Understanding what’s included and what’s excluded can help you organize your records and avoid overpaying.
| Included in Auditable Payroll | Excluded from Auditable Payroll |
|---|---|
| Gross wages and salaries | The overtime premium portion (the extra half of time-and-a-half) |
| Bonuses and commissions | Severance pay |
| Holiday, vacation, and sick pay | Tips and gratuities |
| Employer contributions to Section 125 plans (in CA) | Group insurance and pension contributions |
| The straight-time portion of overtime hours | Uniform and tool allowances |
The overtime exclusion is one of the most commonly missed savings opportunities. If an employee earns $30/hour and works overtime at time-and-a-half ($45/hour), only $30 of each overtime hour counts as auditable payroll. The extra $15 premium is excluded. For businesses with significant overtime, especially in construction, manufacturing, and healthcare, this exclusion can reduce the auditable payroll by thousands of dollars.
To claim the exclusion, you must keep overtime records that show the straight-time rate and the overtime hours for each employee separately. Lump-sum payroll records that don’t break out overtime will not qualify.
How Subcontractors Affect Your Audit
This is where many California employers get blindsided. If you hire a subcontractor who does not carry their own workers’ comp coverage, the auditor will add the amount you paid that sub to your auditable payroll.
The logic: if the sub has no coverage and gets injured on your job, your policy responds. The carrier charges accordingly.
To avoid this:
- Collect a Certificate of Insurance (COI) from every subcontractor before they start work.
- Verify the COI dates cover the entire period the sub works for you.
- Confirm the COI lists workers’ compensation coverage, not just general liability.
- Keep all COIs in your audit folder, organized by subcontractor name and date range.
If a sub’s COI lapses mid-project and you don’t catch it, the uninsured period gets added to your payroll at audit. For a $50,000 subcontract, that could add $5,000 or more in unexpected premium depending on the class code rate.
Common Audit Mistakes That Cost You Money
1. Misclassified employees
An office worker classified under a construction class code will generate a much higher premium than necessary. Conversely, a field worker classified as clerical will trigger a reclassification and back-charges at audit. Review your class codes annually and update them when roles change.
2. Missing overtime records
Without documented overtime breakdowns, the auditor cannot apply the overtime exclusion. Your entire payroll, including all overtime premiums, counts at full value. This is one of the easiest savings to lose.
3. Uninsured subcontractors
Every dollar paid to a sub without a valid COI becomes part of your auditable payroll. On high-rate class codes, this can be extremely expensive.
4. Forgetting to report mid-year changes
If you hired 10 new employees, added a division, or started operations in a new state mid-year and didn’t tell your carrier, the audit will catch it. Reporting changes as they happen avoids large year-end adjustments.
5. Including exempt owners in payroll
If corporate officers or LLC managing members have filed valid exemption waivers, their compensation should not appear in auditable payroll. Make sure the waiver is on file with your carrier before the audit.
How to Dispute an Audit Result
If you believe the audit result is wrong, you have options. Start by requesting a detailed breakdown of the auditor’s findings from your carrier. Common grounds for dispute include:
- Class code misassignment (the auditor put employees in the wrong classification)
- Payroll calculation errors (overtime exclusion not applied, wrong employee included)
- Subcontractor payroll added despite a valid COI being available
- Inclusion of non-auditable compensation (severance, tips, or pension contributions counted as payroll)
If you can’t resolve it directly with the carrier, you can request a voluntary re-audit or file a dispute with the WCIRB. Your insurance broker should help you navigate the dispute process and present your documentation.
Frequently Asked Questions
How often does a workers’ comp premium audit happen?
Once per policy period, typically at the end of each annual term. Some carriers also conduct interim audits mid-year for large or rapidly growing businesses. These are less common but help prevent large year-end adjustments.
What happens if I don’t cooperate with the audit?
Your carrier can estimate your payroll based on the information available, which almost always results in a higher premium than your actual figures would support. In extreme cases, the carrier can cancel or non-renew your policy for failure to cooperate.
Can I owe money after the audit even if I had no claims?
Yes. The audit is about payroll accuracy, not claims. If your actual payroll was higher than the estimate you provided at the start of the policy, you will owe additional premium regardless of your claims history.
How far back can an insurer audit my policy?
Typically, the audit covers only the most recently completed policy period. However, if there is evidence of fraud or material misrepresentation, the carrier or the WCIRB may review prior periods.
Do I need to separate overtime on my payroll reports?
Yes, if you want to claim the overtime exclusion. The auditor can only exclude the overtime premium portion (the extra half of time-and-a-half or the extra of double-time) if your records break it out separately. Without that breakdown, your full gross payroll is auditable.
What if my subcontractor’s COI expired during the project?
The period of the lapse is what matters. If the sub’s workers’ comp coverage was inactive for two months of a six-month project, the auditor will add two months’ worth of payments to your auditable payroll. Verify coverage dates before work starts and track renewal dates during the project.
A clean audit starts with a properly structured workers’ compensation policy. DreamSafe Insurance helps California employers set up the right class codes, document subcontractors, and prepare for audits before they happen. Get a free quote to make sure your next audit goes smoothly.
