A workers comp audit is your insurer's review, after the policy year ends, of what you actually paid your workers and what work they did. The premium you paid during the year was an estimate, so the audit replaces it with the final premium and bills you for the difference or refunds what you overpaid. You agreed to the audit when you bought the policy, and refusing it costs far more than going through it.
An audit does not mean your insurer suspects you of anything. It is how every workers comp policy is settled. The money usually turns less on the payroll you reported than on the people you didn't report, mostly subcontractors, and on the class codes the auditor assigns to each employee. Menlo quotes workers compensation insurance with payroll estimates set to match your real operations.
Workers Comp Premium Audit
A premium audit is your insurer's review of your payroll records at the end of the policy term. It sets your final workers compensation premium from what you actually paid your employees and the work each one did. The insurer bills you for any amount above the estimated premium you paid during the year and refunds any overpayment.
What is a workers comp audit and why is your premium only an estimate?
A workers comp audit replaces the estimated premium you paid with the final premium your actual exposures produce. Workers comp rates are charged per $100 of payroll, so the estimated annual payroll on your policy's information page was only a projection of a year that had not happened yet. The information page is the workers comp version of a declarations page. Payroll also means more than base wages: the policy counts all remuneration, including salary, bonuses, commissions and vacation pay.
The policy says this itself. Part Five, "Premium," states that the premium shown is an estimate and that the final premium is set by actual payroll after the term ends. The insurer can audit your records during the policy period and for up to three years after it ends, so a closed policy is not a finished one. Our workers compensation guide walks through Item 4 of the information page, the rate and classification table.
What does the auditor examine?
The auditor checks three things: how much you paid, who did what work, and whether your subcontractors had their own workers comp. The second test depends on class codes, the numbers that tie each kind of work to a rate, which is why a roofer pays many times more per dollar of payroll than a bookkeeper. Auditors don't rely on your summaries. They use source documents and check them against each other:
| Records requested | What the auditor is testing |
|---|---|
| Payroll journals, quarterly federal payroll tax returns (the 941s), state unemployment returns | That the payroll you report matches what you actually paid and already reported to tax authorities |
| Job descriptions, payroll split by employee and duty | That each employee is in the right class code, and that any split of one person's wages across codes is documented |
| Overtime records | That the extra portion of overtime pay is identified separately, so it can be excluded where your state allows |
| Subcontractor ledger and certificates of insurance | That each subcontractor carried its own workers comp for the whole time it worked for you |
| General ledger, cash disbursements | That no labor cost is hidden outside payroll, in casual labor or 1099 payments |
Two of these tests carry most of the money. If there's no record supporting a payroll split, the auditor puts the whole employee in the highest-rated code that applies. And without a certificate of insurance from a subcontractor, all of that sub's labor cost is assigned to you.
A certificate is one page from your sub's insurer, and it counts only if it names the sub and shows coverage in force for every day the sub worked for you. Have yourself named as the certificate holder so you get notice if the sub's policy is canceled during your job.
What are the most common audit surprises?
Most additional premium comes from three patterns, and paperwork you can collect months in advance prevents all three:
- An uninsured subcontractor becomes your employee: with no valid certificate in the file, the sub's payroll is added to yours at audit. If you can't document that payroll, the auditor charges you on the full contract price. And if you hire an uninsured subcontractor, state law usually makes you the employer of its injured workers anyway, so you carried that injury risk all year regardless.
- The clerical code stops applying: many owners think anyone who works at a desk some of the time falls under the office code (8810). They don't. If an employee coded 8810 also pulls stock or visits job sites, that person goes into the code for most of your operations, the governing classification, and the auditor only needs to see it once.
- Overtime stays in the number: most states let you exclude the premium portion of overtime (the amount above straight time), but only if your records show it separately. Report gross wages in one column and you pay premium on the higher gross figure. Severance works the same way, and so do officers' salaries above your state's maximum.
What happens if you ignore the audit?
Ignoring the audit turns a paperwork issue into a financial one. Refusing to provide records breaks your promise under Part Five, and most policies also carry the Audit Noncompliance Charge Endorsement (WC 00 04 24). Where the state allows it, that endorsement lets the carrier charge a penalty based on your estimated annual premium, commonly up to two times that premium. Check the actual multiplier on your own copy of the endorsement.
California sets a bigger penalty by statute. Under Insurance Code Section 11760.1, an employer that fails to give the insurer access to its records owes a total premium equal to three times the insurer's current estimate of the annual premium, plus the insurer's audit costs once the employer has ignored three requests over at least 90 days.[1] The carrier can also cancel for refusing to cooperate, and that cancellation follows you: the next carrier will know why the last one dropped you.
How do you prepare for a workers comp audit and dispute the bill?
Prepare from the first day of the policy year, not the week before the auditor calls. Summarize payroll by employee, class code and state, keep overtime on its own line, and reconcile it with your quarterly 941 filings every quarter instead of at year end. Collect a subcontractor's certificate before anyone starts work. During the audit, hand over exactly what is asked for and nothing more, because auditors test whatever they receive.
To dispute an audit, first ask for the auditor's worksheets, because arguing with a summary bill goes nowhere. The worksheets show how employees were coded and who was counted as a subcontractor. Send the carrier's premium audit department a written list of each disputed item with evidence attached, and watch the dispute deadline, often 60 days. Pay the undisputed part of the bill while the rest is pending.
If the carrier won't fix a classification, go above it. Class codes are set and enforced by a rating bureau, NCCI in most states and the WCIRB in California, which decides whether a code fits your business. In California, if you disagree with the bureau's decision, Insurance Code Section 11737 lets you appeal to the Insurance Commissioner.[2] Fixing the code matters beyond this bill, because your audited payroll feeds the report that sets your next experience mod, the factor that moves your premium at renewal.
Frequently asked questions
How long after the policy ends can a workers comp audit happen?
Your insurer can audit during the policy period and for up to three years after it ends. Most audits happen within 90 days of expiration, but a carrier can come back later inside that window, so keep payroll records and subcontractor certificates at least that long.
Can a workers comp audit result in a refund?
Yes. Final premium is your actual payroll times the rates, and that math runs both directions. If your audited payroll lands under the estimate you paid, the carrier owes you money back, which is a good reason to finish the audit promptly in a year when the business shrank.
Do 1099 workers need workers comp coverage at audit?
Often yes, at least for premium. The auditor checks your 1099 payments against your state's employment tests. A 1099 worker counts as payroll if they work like an employee, or if they are a subcontractor with no certificate on file. The tax form doesn't decide it. How you work together, and whether you have a certificate, does.
This guide is for educational purposes and summarizes standard NCCI policy language. Your policy's specific terms, conditions, and endorsements control. Talk to a licensed broker about your actual exposures.
How to avoid a surprise audit bill
Collect a certificate from every subcontractor before the job starts, reconcile payroll with your 941s every quarter, and have your broker update the premium estimate at each renewal so the next audit adjustment is small. A workers comp audit replaces the premium you estimated with the premium your actual payroll, class codes and any uninsured subcontractors produce, and those surprises are preventable.
References
- 1.California Legislature. “Insurance Code Section 11760.1.” https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=INS§ionNum=11760.1. ↩
- 2.California Legislature. “Insurance Code Section 11737.” https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=INS§ionNum=11737. ↩