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Uninsured subcontractor audit cost calculator (workers' comp)

A rough estimate for planning only, not a quote, legal advice, or insurance advice. Your carrier's audit rules and your policy decide the real number. Ask your licensed agent or carrier about your situation.

At a workers' comp premium audit, carriers typically count money you paid to a subcontractor who cannot show its own coverage as if it were your payroll, and charge premium on it at the class rate for that kind of work. This calculator multiplies it out so you can see roughly what a missing certificate could add to your audit bill. It works for states where premium is based on payroll, like Idaho. It does not fit Washington, where premium is based on hours worked (see our Washington guide).

Your numbers

The starting values below are made-up example numbers, not typical rates. Replace them with figures from your own records and your policy's declarations page.

Total paid to subs with no valid certificate for the work dates ($) Share of those payments your carrier treats as labor (%)Some carriers let you exclude documented materials, others count the full payment. Use 100 if you don't know. Class rate for the sub's type of work, per $100 of payrollFrom your policy declarations or your agent. Rates vary widely by class code and carrier. Experience modification factor (optional)Shown on your policy if you have one. Use 1.00 if you don't.

How the math works

Estimated added premium = payments to uninsured subs × labor share × (class rate ÷ 100) × experience mod. Real audit bills can differ because of policy minimums, schedule credits or debits, state assessments and surcharges, premium discounts, and how your carrier classifies the work. Some carriers also apply a higher class rate than you expect if the sub's work falls under a different code.

The bigger risk is not the premium

In Idaho, an employer can be liable for workers' comp benefits to an injured worker of a contractor or subcontractor under it that failed to carry required coverage (Idaho Code §72-216). An injury claim can cost far more than the audit charge this page estimates.

How to keep this number at zero

• Collect a current workers' comp certificate, or the sub's exemption documentation, before the first payment. See our Idaho audit guide for which owners are exempt.
• Track expiration dates in our free certificate tracker and keep expired certificates, since the audit covers the whole policy period.
• Before the audit, match every sub you paid to a certificate that covers the work dates, using the printable checklist.

If you're shopping for your own coverage: [AFFILIATE LINK PLACEHOLDER: ERGO NEXT Insurance quote, pending program approval] Comparing quotes from more than one carrier or an independent agent is common practice.

Sources

• Idaho Code §72-216 (Idaho Legislature), checked Nov 2, 2026
• The formula is standard premium arithmetic (rate per $100 of payroll times the experience mod); confirm how your carrier rates uninsured subs.