A workers compensation premium audit feels like an examination of your business. It is not. It is an examination of your file.
The auditor is not forming a judgement about whether you run a good company. They are checking whether payroll matches the classifications, and whether every subcontractor you paid can be shown to have carried their own coverage. Those questions have documentary answers, and the answers were fixed months ago.
Which means the outcome is largely determined before anybody schedules anything. Here is what determines it.
The Subcontractor Certificate Problem
This is the single largest source of surprise assessments for contractors, and the mechanism is simple. A subcontractor who cannot be shown to have carried their own workers compensation coverage generally gets added to your exposure base. You pay premium on their payroll as though they had been your employees.
On a contractor running significant volume through subs, that is not a rounding error. It arrives as one number, at once, after the period it relates to is closed.
The two ways it goes wrong
- Never collected. A sub started quickly, the work went fine, nobody asked. Easy to prevent, impossible to fix afterwards.
- Lapsed mid-job. The certificate was current when they started and expired in month four. This is the more common one, because nothing announces it and the sub is still on site.
The fix for both is the same and it is dull: collect at onboarding, record the expiry date, and chase the renewal before it passes rather than after. It is a clerical task that protects a five figure exposure, which is a ratio worth remembering when deciding whose job it is.
Class Codes Are Not Administrative
Workers compensation rates vary sharply between classifications, because the underlying risk does. A crew carried against a higher-rated code than the work justifies costs money on every payroll run for a full policy year.
Two things follow. Classifications should reflect the work actually being performed, reviewed when what your crews do changes rather than only when the policy renews. And where an employee genuinely works across classifications, some jurisdictions permit payroll to be divided between them, but only where contemporaneous records support the split. Reconstructing that division during the audit generally does not work, because the records were not kept that way at the time.
Overtime, and the Records That Let You Exclude It
In many jurisdictions the premium portion of overtime, meaning the extra above the base hourly rate, may be excluded from the audit base. The condition is documentary: payroll records have to show the premium portion separately rather than reporting one gross figure.
This is a payroll setup decision made once that saves money every year afterwards, and a records gap that simply forfeits it. Rules vary by state, so confirm what applies where you operate rather than assuming the treatment carries across jurisdictions.
The Classification Question Underneath All of It
Separately from premium audits, there is the larger question of whether someone you treat as a subcontractor is genuinely independent.
That turns on how the work is actually directed rather than on what an agreement says. Direction, scheduling, who supplies the tools, and who carries the business risk all weigh on it. Construction gets examined closely, and a reclassification reaches back across prior periods with payroll taxes, interest and penalties attached.
It is a legal determination rather than a bookkeeping one, and the genuinely close calls are worth putting in front of a specialist rather than settling internally. What bookkeeping contributes is the record: W-9s, certificates, contracts and payment history that show the arrangement was what you say it was.
Build the Package Before the Notice
When the audit notice arrives, the useful work is assembly and review, not collection. Everything you can still collect at that point is everything you already had.
- Payroll registers for the period, split by classification.
- The subcontractor list with certificates covering the exact periods each one worked.
- Overtime records showing the premium portion separately.
- Job records supporting how work was classified.
- Your own certificates and the policy declarations for the period.
Review it for gaps yourself first. A gap you find is occasionally still closeable. A gap the auditor finds is a number.
Nothing here is jurisdiction-specific advice. Classification rules, payroll division, overtime treatment and audit procedure vary by state and by carrier. Confirm what applies to your policy and your states before relying on any of it.
This runs as part of the compliance substrate rather than as an annual event. It is described on the workers comp audit support page, and the document collection side sits with subcontractor compliance. For the wider record keeping picture see what records a contractor has to keep.
Frequently Asked Questions
What happens at a workers comp premium audit?
The carrier reviews your actual payroll for the policy period against what you estimated when the policy was written, and against the classification codes assigned to each worker. Premium is recalculated on the real figures, which can produce a bill or a refund. The auditor also reviews payments to subcontractors, and any sub who cannot be shown to have carried their own coverage is generally added to your exposure base, meaning you pay premium on their payroll as though they were your employees.
How do I keep subcontractor payroll out of my workers comp audit?
By holding a current certificate of insurance for every subcontractor covering the entire period they worked for you. The two failure modes are a sub who never provided one and a sub whose certificate lapsed part way through the job, and the second is more common because nothing announces it. Collect at onboarding, track the expiry date, and collect the renewal before it passes. A certificate obtained after the audit notice generally does not help for the period it did not cover.
Do class codes really change what I pay?
Substantially. Workers compensation rates vary sharply between classifications, and a crew recorded against a higher-rated code than the work justifies costs real money across a full policy year. The classifications have to reflect the work actually performed and the records have to support the split. Where an employee genuinely works across classifications, some jurisdictions permit division of payroll, but only where contemporaneous records show it. Reconstructing that at audit does not usually work.
Can overtime be excluded from a workers comp audit?
In many jurisdictions the premium portion of overtime, the extra above the base rate, may be excluded from the audit base. The condition is that payroll records show it separately rather than reporting a single gross figure. This is a case where a payroll setup decision made once saves money every year, and where a records gap simply forfeits the reduction. Rules differ by state, so confirm what applies where you operate.
What should I do when the audit notice arrives?
Assemble the package before the appointment rather than during it: payroll registers split by classification, the subcontractor list with certificates covering their working periods, overtime records showing the premium portion, and your job records supporting how the work was classified. Review it for gaps first, because a gap you find yourself is sometimes still fixable and a gap the auditor finds is not. Treating the audit as a document exercise rather than a conversation is the whole discipline.
The Audit Is Decided by the File, Not the Conversation
Workers compensation and general liability premium audits are settled by documentation that either exists or does not. Class codes recorded correctly through the year, current certificates on every subcontractor, and overtime separated in the payroll records. None of it can be assembled after the notice arrives, which is why the work is a monthly habit rather than an annual scramble.
About the Author
Tom Woolley, MBA
Tom Woolley is a fractional CFO who spent six years running job costing and logistics in construction before founding Today CFO. He works with commercial subcontractors and small general contractors on the reporting a GC and a surety actually read.
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