Workers' Comp Premium Audit Guide

Workers' comp premium is calculated on payroll, and payroll is an estimate at the time you buy the policy — you don't know exactly what you'll pay employees over the next twelve months, and your operations or headcount might change. The premium audit is the mechanism that reconciles the estimate against reality: it looks at your actual payroll by class code, actual employee count, and actual subcontractor payments during the policy period, and adjusts your final premium to match what those numbers should have produced.

This is a standard, expected part of how workers' comp works, not a special review reserved for businesses the carrier is suspicious of. Every policy, from the smallest owner-operator to the largest employer, goes through some version of this reconciliation, because the entire pricing model depends on the estimate at the start being checked against reality at the end.

Most policies are audited annually, shortly after the policy period ends, though some carriers audit quarterly or monthly for larger accounts or under pay-as-you-go arrangements (see our guide to pay-as-you-go workers' comp). The audit can be conducted by mail, phone, or in person, depending on your carrier, your policy size, and the complexity of your operations.

A mail or phone audit typically asks you to submit payroll figures and supporting documents yourself, which is faster but places more responsibility on you to organize the information accurately. An in-person audit involves an auditor reviewing records and sometimes observing operations directly, which tends to happen for larger or more complex accounts where a document review alone wouldn't give a complete picture.

A typical audit reviews:

The single biggest factor in how smoothly an audit goes is whether your payroll records are organized by class code before the auditor asks for them. Have your payroll register, your subcontractor certificates of insurance, and a short written description of any operational changes during the year ready to go. If you have employees doing more than one kind of work, being able to show how their time split between duties supports rating them under multiple class codes instead of defaulting everyone to the highest-rated code.

It also helps to designate one person on your team as the point of contact for the audit, ideally someone who actually has access to payroll records and knows the operational details, rather than routing the auditor's questions through several people. A single knowledgeable point of contact tends to produce a faster, more accurate audit than a scattered response across multiple staff members.

If actual payroll came in higher than estimated, or if operations shifted into a higher-rated class code, you'll typically owe an additional premium. If actual payroll came in lower, or subcontractor payroll you'd budgeted for turned out to be verified as separately insured, you may receive a credit. Because the experience mod and future premium estimates are both influenced by audited figures, an audit isn't just a one-time reconciliation — it feeds into how your next policy period is priced. This is also why your next policy's estimated payroll is usually based on your most recent audited figures rather than starting from scratch each renewal.

If an audit result doesn't match your own records, most carriers have a formal dispute or review process — start by requesting the auditor's worksheet and comparing it line by line against your payroll records and any subcontractor certificates on file. Common, legitimate dispute points include a subcontractor's payroll being included despite a valid certificate of insurance on file, overtime rated at the full rate instead of the straight-time equivalent, or an employee's duties being coded at the wrong classification. Keep documentation, and raise disputes promptly — most carriers set a window for review requests after the audit bill is issued, and missing it can mean losing the chance to correct a genuine error.

A premium audit is about reconciling payroll and classification against actual operations, not about investigating claims, evaluating safety practices, or deciding coverage eligibility going forward. It's easy to conflate an audit with a broader review of your account, but the auditor's job is narrower than that: verify what actually happened during the policy period against what was assumed at the start, and adjust the bill accordingly. Any separate underwriting concerns your carrier has would typically come up at renewal, not through the audit process itself.

Reviewing your estimated payroll mid-year, keeping subcontractor certificates current, and understanding your own class codes (see our class codes guide) all reduce the size of the swing at audit time. If audits consistently produce large adjustments, that's often a sign your original estimate or class code mix needs a closer look before your next renewal — something a comparison across carriers can also surface. Get Multiple Quotes within minutes to see how your actual operations are rated elsewhere, using the real payroll and class code detail from your most recent audit rather than a fresh guess.