What Is a Workers’ Comp Premium Audit? A Contractor’s Plain-English Guide

If you just opened a letter saying your workers’ comp policy is being “audited,” don’t panic — it’s routine, and it happens to every policy. But it’s also where contractors get blindsided by a bill they didn’t budget for. Here’s exactly what it is and how to walk in prepared.

The one-sentence version

When you bought your policy, the premium was an estimate based on the payroll you projected for the year. The premium audit is the carrier going back after the policy period to check what you actually paid out — and adjusting the premium up or down to match. You’re not being singled out; the estimate just gets trued up.

Why it happens every single year

Workers’ comp premium is built on payroll: your wages, by class of work, times a rate. Nobody knows their exact payroll a year in advance, so the carrier prices off a forecast and reconciles at the end. No audit, no way to know if you owe more or they owe you a refund. So it’s baked into every policy.

What the auditor actually checks

It comes down to four areas — the same four every time:

• Payroll — reconciled against your 941s, W-2/W-3, and state filings.
• Subcontractors — anyone you paid who can’t document their own coverage can be added to your payroll. This is where most surprise bills come from.
• Owner/officer payroll — often capped or excludable, but auditors may drop the full salary in by default.
• Classification — whether your people are coded to the right (and not an inflated) class.

Want the full prep list? See the contractor’s audit checklist.

Physical, phone, or mail

Audits come in three flavors: a physical audit (an auditor visits and reviews records), a phone/virtual audit, or a mail/voluntary audit (you fill out a form and attach documents). Smaller policies usually get mail or phone. Either way the documents they want are the same — and the cleaner yours are, the less they have to assume.

The two outcomes — and the one that surprises people

The audit ends one of two ways: you owe additional premium, or you get a return premium (a refund or credit). Contractors brace for the bill but forget the refund is possible too — if you overpaid on overtime, owner payroll, or classification, you may be owed money. That’s why you read the worksheet instead of just paying.

How to come out even instead of behind

The whole game is documentation: collect subcontractor certificates up front, keep payroll broken out, and know your owner cap. The single biggest lever is sub coverage — run your subs through the free COI Gap Checker to see who’d get added to your payroll, then estimate your exposure with the calculator before the auditor does.

General information for contractors, not legal or insurance advice. Audit procedures and rules vary by state and carrier — confirm yours.