How to Prepare for a Workers' Comp Premium Audit

Workers' compensation insurance is not priced on a fixed premium. It is an estimate paid in advance and settled after the policy year ends. Every year, your carrier sends an auditor — in person or by mail — to verify that your actual payroll, your actual job classifications, and your actual subcontractor management matched what was projected when the policy was written.

The audit happens whether you are ready or not. The outcome — a refund or a supplemental premium bill — is largely determined by how organized your records are and whether you have been managing your classifications correctly throughout the year.

Why the Audit Exists

When you purchase workers' comp coverage, the insurer sets your premium based on estimated payroll for each job classification code multiplied by the rate for that code, then adjusted by your experience modification rate (EMR). Classification codes matter because different types of work carry different risk levels and therefore different rates. Carpentry (5403), concrete work (5213), and electrical work (5190) all carry different rates.

The premium audit reconciles the estimate with reality. If actual payroll was higher than estimated, you owe additional premium. If lower, you receive a credit. If workers were performing work coded at a lower rate than their actual duties, the auditor reclassifies them and charges the difference.

Most premium audits result in additional charges rather than refunds. Payrolls tend to grow in active years, and classification errors run predominantly in one direction.

The Two Biggest Audit Issues

Payroll misclassification is the most common and most expensive problem. Class codes must reflect what workers actually do — not their job title, not how they were originally hired, but what they spend their time doing. A laborer who does 40% framing and 60% concrete work may need to be split across codes or classified at the higher-rated code depending on state rules. Workers who perform multiple types of work must be tracked separately, or the carrier applies the highest applicable rate to all of their payroll.

Missing certificates of insurance from subcontractors is the other major issue. When you hire a subcontractor who cannot produce a valid certificate of insurance showing workers' comp coverage, their payroll gets added to yours at the applicable rate for that type of work. The auditor will request COIs for every subcontractor used during the policy year. A single missing certificate — even for a sub who worked two weeks on your project — can result in an audit adjustment that exceeds what you paid them.

What Auditors Ask For

Be prepared to provide:

Payroll records broken out by classification: Payroll must be separated by the type of work actually performed, not by employee name or title. If your payroll system does not track hours by work type, reconstruct this from time records, job cost reports, or daily logs.

Certificates of insurance for all subcontractors: Each COI must be current for the dates the sub performed work. Expired certificates are treated the same as missing ones.

Officer exclusion or inclusion forms: Corporate officers in many states can elect to exclude themselves from coverage. If your officers are excluded, the election forms must be on file with your carrier and current for the policy year.

Contracts or work orders for subcontractors: Documents showing what each sub was engaged to do support the classification applied to their work and demonstrate they were operating as legitimate subcontractors.

Payroll summary by project and state: If you worked in multiple states, payroll for each state must be tracked separately. Workers' comp is state-regulated, and rates vary by state.

How to Prepare Before the Auditor Arrives

Start at the beginning of the policy year, not when the audit notice arrives.

Collect COIs at contract signing: No subcontractor starts work without a current certificate on file. Track expiration dates and request renewals when certificates expire mid-project. A spreadsheet works. The cost of this process is trivial compared to the cost of one uncovered sub.

Reconcile classifications quarterly: Payroll departments classify workers at hiring and rarely revisit it. Quarterly reviews — comparing what code the payroll system shows against what the employee is actually doing — catch drift before it accumulates into a year-end problem. A worker originally classified as a laborer who has been doing carpentry for six months should be reclassified before audit time.

Maintain a clean subcontractor file: One folder per sub — physical or digital — with their COI, their contract or work order, and a log of the dates they worked. When the auditor asks, you hand over the file.

Disputing Audit Results

If you disagree with audit findings, most states provide 60 to 90 days to dispute them formally. The process varies by carrier but generally involves:

• A written request for re-audit or detailed explanation of the findings
• Documentation supporting your position on classification or COI status
• Review by the carrier's audit department or, for classification disputes, the applicable rating bureau

Document everything before the window closes. If you believe a worker was correctly classified and the auditor reclassified them, written job descriptions, time records, and contracts describing the work are your evidence. Disagreement without documentation is rarely persuasive.

The EMR Connection

Premium audits affect the current policy year's premium. Your experience modification rate — the multiplier applied to your base rate — is calculated separately using three prior years of loss data from NCCI or your state's rating bureau.

A clean audit does not directly lower your EMR. But misclassification that puts workers in incorrect codes can distort your loss ratios in ways that affect future EMR calculations. Accurate classification is the foundation of accurate experience rating over time. Contractors who manage their classifications carefully tend to have their EMR calculated on a basis that reflects their actual risk profile, rather than one inflated by administrative errors.