Workers' compensation premiums are estimates. The audit at the end of the policy year calculates what the client actually owes — and the difference can be significant if payroll grew or job classifications weren't accurate.
Workers' compensation premiums are based on estimated payroll at the start of the policy year. The carrier makes a calculation, sets a deposit premium, and the policy runs. At the end of the year, an auditor reviews actual payroll records — and the final premium is recalculated based on what the business actually paid out.
For clients who had a good year — hired more people, ran more overtime, or expanded into new work — the audit can produce an additional premium bill they were not expecting. For agents, this is one of the more common reasons a client calls frustrated after a policy year ends.
What Drives the Audit Number
Two things determine the audit result: actual payroll and job classifications.
Payroll is straightforward — if the client hired more employees or paid more overtime than the estimate projected, the premium goes up proportionally. But classification errors are where audits get complicated.
Workers' compensation rates vary significantly by job classification. An office worker and a roofer on the same payroll are priced very differently because the risk of injury differs. When an employee's actual duties don't match the classification on the policy — either because the job evolved or because it was classified incorrectly at the start — the auditor may reclassify the work, sometimes retroactively changing the rate applied to that payroll.
When the Client Grows
A client who expands operations mid-year may not realize they need to notify you. They hired a crew, took on a larger contract, or added a new type of work — and the policy's estimated payroll is now well below reality. The audit resolves that gap, but the resulting bill can strain cash flow if the client wasn't prepared.
Building in a mid-year payroll check with commercial clients — particularly those in growth mode — can head off audit surprises before they happen. A quick call to update the estimated payroll costs nothing and prevents the frustration of a large year-end bill.
Classification Disputes
If an audit results in a classification change the client believes is incorrect, it can be disputed. The process varies by carrier, but it generally involves providing documentation of the employee's actual duties. Classification disputes take time and are not guaranteed to succeed, but they are worth pursuing when the auditor's determination doesn't accurately reflect the work being done.
Your role is to make sure the client understands the dispute process and has the documentation needed to support their position.
Setting Expectations at Binding
The most effective thing you can do is explain the audit process when the policy binds. Clients who understand upfront that workers' comp is an estimate — and that payroll growth means a larger final premium — are far less likely to be blindsided. A brief explanation at the start of the policy year turns a surprise into an expected outcome.
For any commercial client with employees, the audit conversation is worth having once a year. It keeps the relationship intact when the bill arrives.