Workers Comp Premium Audit
Also known as: WC Audit, Year-End Audit
Mandatory for nearly all WC policies. Under-reported payroll triggers back-bill at audit time (common owner-surprise scenario). Pay-as-you-go billing eliminates audit surprises by calculating weekly from actual payroll.
Real-world scenario
Cedar Ridge Framing LLC, a residential carpentry contractor, bought a workers compensation policy at renewal based on an estimated annual payroll of $850,000. At the carpentry NCCI class code rate of $7.20 per $100 of payroll, that produced a $61,200 manual premium, adjusted by the firm's experience modifier of 1.15 to a $70,380 deposit. Cedar Ridge paid $17,595 down (25%) and financed the balance in monthly installments of about $5,278.
Because construction had a strong year, the actual work far exceeded the estimate. When the year closed, the carrier's premium audit examined payroll records, tax filings, and certificates of insurance. Auditable payroll landed at $1,020,000 — not $850,000. The auditor also found $180,000 paid to an uninsured drywall subcontractor with no valid certificate, which was reclassified into Cedar Ridge's own carpentry payroll, adding another $12,960 in manual premium. Overtime of $96,000 got the required one-third premium portion excluded under payroll limitation, removing $32,000 from the auditable base and saving roughly $2,650 after the modifier.
Netting those adjustments, the auditable base came to $1,168,000 ($1,020,000 actual + $180,000 uninsured sub − $32,000 overtime exclusion). At $7.20 per $100 that is an $84,096 manual premium, and with the 1.15 modifier the audited premium reached $96,710 against the $70,380 deposit — so Cedar Ridge owed an additional $26,330, billed in one lump sum 30 days after the audit. Had the year come in light instead, the same process could have generated a refund of several thousand dollars. The owner learned to true-up estimated payroll mid-term and keep subcontractor certificates on file to avoid a surprise five-figure bill.
How it affects your premium
A workers comp premium audit does not set a rate — it reconciles the estimated exposure basis against what actually happened during the policy term. The size of the additional bill or refund is driven by:
- Actual vs. estimated payroll — the single biggest lever; every extra $100 of auditable payroll is multiplied by your class code rate.
- Uninsured subcontractors — payments to subs who cannot produce a valid workers comp certificate are added to your payroll and charged at your rate.
- Class code assignment — misclassified employees (e.g., a laborer coded as clerical) get reclassified to the correct, often higher, code at audit.
- Overtime and payroll caps — overtime premium portions and executive-officer minimum/maximum caps reduce or adjust the auditable base when documented properly.
- Experience modifier — your experience modifier is applied on top of audited exposure, so a mod above 1.0 amplifies any payroll increase.
- Record quality — missing certificates, incomplete payroll registers, or no overtime breakout force the auditor to charge the highest defensible figure.
Common misconceptions
Myth: The premium I paid at the start of the policy is the final price.
Reality: That is only a deposit premium based on estimated payroll. The audit trues it up to actual exposure, so you may owe more or receive a refund at year-end.
Myth: An audit can only cost me money.
Reality: Audits go both ways. If your actual payroll came in below the estimate, the audit generates a return premium refund rather than an additional bill.
Myth: Payments to subcontractors are never my responsibility.
Reality: If a subcontractor cannot show a valid workers comp certificate, the auditor adds those payments to your payroll and charges premium on them — treating the sub's workers as if they were yours.
Myth: Ignoring the audit request makes it go away.
Reality: Non-compliance typically triggers an estimated audit that assumes a large payroll increase, plus possible penalties and non-renewal. Cooperating almost always yields a lower, defensible number.
Frequently asked questions
What records will the auditor ask for?
How is overtime handled in a workers comp audit?
Why did I get an additional premium bill after my policy ended?
Can I dispute the audit findings?
How can I avoid a large audit bill next year?
Sources cited
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