Last updated: July 2026
An insurance premium audit reconciles the payroll or sales your policy was priced on against your actual figures at the end of the term, then bills the difference or issues a refund. Contractor bills most often jump for one reason: uninsured subcontractors get charged as your own payroll, work gets assigned to a higher-rated class code, or records are missing so the auditor estimates high. You can dispute a final audit by supplying the correct documents.
Why a premium audit can hand you a surprise bill
Your workers’ compensation and general liability premiums are not final when you buy the policy. They are an estimate, priced on the payroll or sales you expected for the year. At the end of the term the carrier runs a premium audit to compare that estimate against what actually happened. If your real exposure was higher than estimated, you owe additional premium. If it was lower, you may get a refund.
That reconciliation is where the surprise comes from. A contractor who grew, took on more subs, or kept loose records can open the mail to a bill for thousands of dollars nobody budgeted for. The good news: the increases are almost always traceable to a handful of specific causes, most of them preventable, and a final audit can be disputed. This guide walks through why the bill jumps and what to do about it.
What your premium is actually based on
To understand why a bill moves, you have to know what each policy is rated on. They are not the same.
| Policy | Rated on | What that means at audit |
|---|---|---|
| Workers’ compensation | Payroll, per $100, by class code | Under the NCCI Basic Manual, WC premium is your payroll divided by 100, times the rate for each class code. More payroll, or payroll in a higher-rated code, means more premium. |
| General liability | Gross sales or payroll, depending on the class | Some GL classes are rated on gross receipts; contractor and labor classes are frequently rated on payroll. Many general contractors who subcontract most of their work are on payroll-based GL. |
One useful detail on the workers’ comp side: for overtime, only the premium portion of the pay is excluded from payroll, the extra half of time-and-a-half, not the whole overtime check. You have to keep overtime records to claim even that. A few states, including Pennsylvania and Delaware, do not allow the overtime premium portion to be removed at all.
The four things that blow up a contractor’s audit bill
When a contractor’s premium jumps at audit, it is nearly always one of these. Knowing which one is happening tells you whether you can fight it.
1. Uninsured subcontractors charged as your payroll
This is the biggest one. If you paid a subcontractor and cannot produce a valid certificate of insurance for them, the auditor treats that payment as if it were your own payroll. Travelers states it directly: without a valid certificate of workers’ compensation insurance, the carrier may charge a premium for the work performed by an independent contractor or subcontractor. A single uninsured sub you paid $80,000 can be added straight to your auditable payroll. See our full guide to subcontractor insurance requirements and how to collect the certificates that prevent this.
2. Work assigned to a higher-rated class code
Every worker’s pay is assigned to a class code, and codes carry very different rates. If you cannot show records that split an employee’s duties, the auditor will assign all of that person’s payroll to the highest-rated code that applies. An office employee whose pay lands in a roofing code, for example, is a large, avoidable increase.
3. Missing or incomplete records
An audit runs on documentation. When the payroll, overtime, or subcontractor records the auditor needs are missing, the auditor does not give you the benefit of the doubt: they estimate, and the estimate defaults to the highest applicable rate. Good records almost always produce a lower number than an auditor’s estimate.
4. 1099 contractors treated as employees
Paying someone as a 1099 does not shield you at audit. If a 1099 contractor did work for you and has no coverage certificate of their own, those payments are added to your exposure the same way an uninsured sub’s are. The paperwork, not the tax form, decides how the payment is treated.
What to have ready before the audit
An audit can be a physical visit, a mailed self-report form, or a phone call. Whichever format your carrier uses, having these ready is the difference between a clean audit and an estimated one. Auditors typically ask for:
- Payroll reports and your payroll journal for the policy period
- Federal 941s and state unemployment wage reports
- 1099s and business tax filings (Schedule C, 1120, or 1065)
- Certificates of insurance for every subcontractor, covering the dates they worked for you
- Check register or cash-disbursements journal showing payments to subs, casual labor, and materials
- Overtime records, so you can claim the overtime premium-portion exclusion on workers’ comp
- Job descriptions or duty notes that support the correct class code for each worker
The single highest-value item on that list is the stack of subcontractor certificates. Building a subcontractor compliance system that collects them as work is awarded, not scrambled together at audit time, is what keeps the biggest surprise off your bill.
How to dispute a premium audit
A final audit is not automatically the last word. Carriers have a process to review and revise an audit, and contractors use it regularly. If your bill looks wrong, do this:
- Read the audit worksheet, not just the invoice. The worksheet shows how the auditor classified payroll and which subcontractor payments were added. That is where errors hide.
- Identify which of the four causes drove the increase. Uninsured subs, a wrong class code, an estimate from missing records, or 1099 treatment. Each has a different fix.
- Gather the documents that correct it. Late-arriving subcontractor certificates, payroll records that split duties into the right code, or overtime records you did not submit the first time.
- Send a written request for review to the carrier’s premium audit department, stating the reason and attaching the supporting documents. Carriers such as EMPLOYERS accept exactly this kind of written revision request.
This is also where an independent broker earns their keep. We read the worksheet with you, find the reversible items, and package the dispute so it lands as a revision rather than a rejected complaint.
How to keep next year’s audit clean
The best dispute is the one you never have to file. Everything that blows up an audit bill is preventable with a few habits kept up during the year, not scrambled together the week the audit notice arrives:
- Collect a certificate from every sub before they start, and a renewal certificate if their policy renews mid-project. This single habit removes the largest surprise. Our subcontractor compliance page has a step-by-step system.
- Keep payroll split by duty, so an employee who does two kinds of work is not defaulted into the highest-rated class code.
- Track overtime separately, so you can claim the overtime premium-portion exclusion on workers’ comp.
- Estimate your payroll and sales honestly at renewal. Lowballing the estimate to get a cheaper policy just moves the bill to audit time, with no interest-free benefit.
- Report mid-year growth to your broker. If you add crews or take on a big job, a payroll endorsement now avoids a large lump sum at audit.
An independent broker who quotes you to the right class codes and limits from the start, and who helps you keep sub certificates current, is how most contractors turn a yearly surprise into a predictable line item.
Key takeaways
- Your premium is an estimate; the audit reconciles it to actual payroll or sales and bills the difference.
- Workers’ comp is rated on payroll; contractor general liability is often payroll too, sometimes gross sales.
- The bill jumps for four reasons: uninsured subs charged as your payroll, higher-rated class codes, missing records forcing an estimate, and 1099s with no certificate.
- Keep subcontractor certificates, payroll, 941s, overtime, and duty records; the certificates prevent the biggest surprise.
- A final audit can be disputed: read the worksheet, correct the cause with documents, and send a written revision request.
Frequently asked questions
What is an insurance premium audit for contractors?
It is the process where your insurer reconciles the estimated payroll or sales your policy was priced on against your actual figures for the term. If your real exposure was higher than estimated, you owe additional premium; if it was lower, you may receive a refund. Workers’ compensation and general liability policies are both commonly audited.
Why did my insurance premium increase at audit?
For contractors, an increase almost always traces to one of four causes: you paid a subcontractor without a valid certificate of insurance and it was charged as your own payroll, a worker’s pay was assigned to a higher-rated class code, records were missing so the auditor estimated high, or a 1099 contractor with no coverage certificate was added to your exposure. Identifying which one occurred tells you whether it can be reversed.
Is a premium audit based on payroll or revenue?
It depends on the policy. Workers’ compensation is rated on payroll, per $100 of payroll by class code, under the NCCI Basic Manual. General liability can be rated on gross sales or on payroll depending on the class; many contractor and general-contractor policies are payroll-based, especially for GCs who subcontract most of their work.
Can I be charged for a subcontractor’s insurance on my audit?
Yes. If you paid a subcontractor and cannot produce a valid certificate of insurance for them at audit, the auditor treats those payments as your own payroll or exposure and charges premium for them. Travelers states that without a valid certificate of workers’ compensation insurance, the carrier may charge a premium for work performed by a subcontractor. Keeping valid certificates on file prevents this.
Do 1099 contractors get added to my premium audit?
They can. Paying someone as a 1099 does not automatically keep them off your audit. If a 1099 contractor did work for you and has no coverage certificate of their own, the auditor can add those payments to your auditable exposure, the same way an uninsured subcontractor is added. The certificate, not the tax form, determines the treatment.
How do I dispute a premium audit I think is wrong?
Start with the audit worksheet, not the invoice, and find which cause drove the increase. Gather the documents that correct it, such as a subcontractor’s certificate for the work dates, payroll records that split duties into the right class code, or overtime records. Then send a written request for review to the carrier’s premium audit department with the supporting documents attached. Carriers have a defined revision process for this.
What records will the auditor ask for?
Typically payroll reports and your payroll journal, federal 941s and state unemployment wage reports, 1099s and business tax filings, certificates of insurance for every subcontractor covering their work dates, a check register or cash-disbursements journal, overtime records, and job descriptions to support class-code assignments. Having these ready is the difference between a clean audit and an estimated one.
How is overtime handled in a workers’ comp audit?
Only the premium portion of overtime pay, the extra half of time-and-a-half, is excluded from payroll, and you must keep overtime records to claim it. The regular-rate portion of overtime stays in payroll. A few states, including Pennsylvania and Delaware, do not allow the overtime premium portion to be removed at all.
What are the different types of premium audit?
There are three common formats: a physical audit conducted on-site, a mail or voluntary audit where you complete a self-report form, and a phone audit. The records the auditor needs are the same regardless of format, so the preparation is the same.
Sources
Facing an audit bill, or want to prevent the next one?
ContractorsInsured.net is a licensed insurance brokerage (CA Lic #6015321, TX Lic #3305690). Send us your audit worksheet and we will read it with you, find the reversible items, and package the dispute; or let us quote you to the right class codes and limits so next year’s audit holds no surprises.
This guide is general information for contractors, not legal, tax, or insurance advice. Audit rules vary by policy, class, carrier, and state; confirm specifics with your broker or carrier.