How Does a Workers’ Compensation Audit Work?

A workers’ compensation audit compares the payroll and business information estimated at the start of a policy with the contractor’s actual results.

The insurer reviews payroll, employee duties, business owners, and subcontractor records. It then recalculates the premium for the completed policy period.

If the contractor had more exposure than estimated, the insurer may issue an additional premium bill. If the exposure was lower, the contractor may receive a refund or account credit.

A workers’ compensation audit is not an investigation of an injury claim. Its main purpose is to calculate the correct insurance premium.

Workers’ Compensation Audits at a Glance

Question	General answer
Why is the audit performed?	To replace estimated exposure with actual exposure
When does it happen?	Usually after the policy period ends
What does the insurer review?	Payroll, employee duties, owners, subcontractors, and business operations
Can the audit happen during the policy?	Some insurers can conduct interim audits
Can it be completed remotely?	Often, depending on the insurer and policy
Can the premium increase?	Yes, if actual exposure was higher
Can the contractor receive money back?	Yes, if actual exposure was lower
Are subcontractors reviewed?	Yes, especially in construction
What happens without records?	The insurer may issue an estimated audit
Can the contractor dispute the result?	Usually, through the insurer and applicable state process

The California Department of Insurance explains that a policy’s final premium cannot be determined until the policy period ends and payroll records are audited.

Why Workers’ Compensation Policies Are Audited

Workers’ compensation premiums usually begin with estimates.

When a contractor applies for coverage, the insurer may ask for estimated:

Annual payroll
Number of employees
Employee job duties
Business locations
Owner information
Subcontractor costs
States where employees will work

However, construction businesses often change during the year.

A contractor may hire employees, win larger projects, or expand into another trade. The company may also reduce payroll or use fewer workers than expected.

The final audit replaces those estimates with actual figures. California guidance states that higher actual payroll can produce additional premium. Lower payroll can create a return premium.

When Does the Audit Take Place?

The final audit usually begins after the policy expires or is canceled.

The insurer may contact the contractor by email, mail, telephone, or an online portal. The notice should explain the deadline and required documents.

Some insurers complete audits remotely. Others may request an onsite review.

NYSIF, New York’s state insurance fund, allows workers’ compensation payroll verification to take place onsite or remotely.

An insurer may also conduct an interim audit while the policy remains active. California notes that insurers generally reserve the right to audit during the policy and for a period after it ends.

Step 1: The Insurer Sends an Audit Request

The contractor first receives a request for payroll and business records.

The notice may identify:

Policy period
Audit deadline
Auditor’s contact information
Required documents
Submission method
Scheduled appointment

The contractor should respond promptly. Delaying the audit can create an estimated bill and may complicate future coverage.

Before sending sensitive records, confirm that the request came from the insurer or its authorized audit company.

Step 2: The Contractor Collects Business Records

The auditor needs enough information to confirm payroll and employee classifications.

Common records include:

Payroll registers
Payroll journals
Individual earnings reports
Quarterly payroll tax returns
Federal Form 941
State unemployment reports
W-2 and W-3 forms
1099 and 1096 forms
General ledger
Cash disbursement records
Check registers
Timecards
Job-cost reports
Employee job descriptions

WCIRB explains that an audit may review payroll registers, earnings reports, timecards, job records, and federal or state quarterly payroll reports.

The records should cover the exact policy period. Calendar-year totals may not match a policy that began in the middle of the year.

Step 3: The Auditor Verifies Total Payroll

The auditor compares payroll records with tax reports and accounting documents.

This step helps identify:

Unreported employees
Bonuses and commissions
Overtime
Cash labor
Payroll changes
Payments made outside the regular payroll system
Differences between accounting and tax records

The auditor does not simply copy one payroll total. Instead, the auditor determines which compensation counts under the applicable workers’ compensation rating rules.

Contractors should provide complete records. They should also explain any difference between payroll reports and tax filings.

Step 4: The Auditor Reviews Class Codes

Class codes group workers according to their operations and job risks.

A construction company may have separate classifications for:

Roofing
Plumbing
Electrical work
Carpentry
Painting
Excavation
Clerical office work
Outside sales
Construction supervision

The auditor compares the policy classifications with the work employees actually performed.

For example, an employee listed as clerical may have visited jobsites and supervised crews. That employee may not qualify for a clerical classification.

California’s Department of Insurance explains that workers’ compensation premiums depend on the employer’s operations and the rates assigned to its classifications.

Can Payroll Be Divided Between Class Codes?

Sometimes, an employee performs more than one type of construction work.

The contractor may be able to divide payroll between classifications when state rules allow it. However, detailed time records are usually essential.

Useful records may show:

Employee name
Date
Hours worked
Job location
Type of work
Payroll assigned to each operation

Without reliable records, the insurer may assign payroll to the applicable higher-rated classification.

Step 5: The Auditor Reviews Owners and Officers

The audit also checks how the policy treats business owners.

Depending on state law and business structure, the policy may include or exclude:

Sole proprietors
Partners
LLC members
Corporate officers

The auditor may request ownership records and exclusion endorsements.

A contractor should not assume the owner is excluded simply because no regular salary was paid. Some states use a set payroll amount for covered owners.

Likewise, a verbal request to exclude an owner may not be enough. The policy should contain the required election or endorsement.

Step 6: The Auditor Examines Subcontractors

Subcontractors are one of the most important parts of a construction audit.

The auditor may request:

Subcontractor agreements
Certificates of insurance
Workers’ compensation policy details
Owner exemption documents
Contractor licenses
Invoices
Payment records
Description of work performed

NYSIF states that construction auditors review contracts, bills, and invoices to verify work performed by policyholders and subcontractors. It also states that charges for employees of uninsured subcontractors can become the policyholder’s responsibility.

New York’s Workers’ Compensation Board warns that insurers often assess general contractors for subcontractor exposure unless the subcontractors provide proof of their own coverage.

Why a Certificate Matters

A workers’ compensation certificate can show that the subcontractor had its own policy.

However, the certificate should:

Match the subcontractor’s legal name
Cover the dates work was performed
Show workers’ compensation coverage
Apply in the correct state
Come from a valid insurer or agent

A certificate that expired halfway through the project may not protect the entire period.

What If the Subcontractor Had No Policy?

The insurer may include some or all subcontractor labor in the contractor’s audit exposure.

The applicable class code may reflect the type of work performed.

For example, payments to an uninsured roofing subcontractor may be treated differently from payments to an insured accounting service.

The final result depends on state rules, available records, and the working relationship.

Step 7: The Auditor Reviews Business Operations

The auditor may ask the contractor to describe the business.

Questions may cover:

Services performed
Trades performed by employees
Work subcontracted to others
Locations
New operations
States of work
Employee supervision
Tools and equipment
Changes during the policy period

This discussion helps the auditor determine whether the classifications still match the company’s operations.

For example, a contractor may have started the year performing interior painting. Later, the company may have added roofing work.

That change could affect both classifications and premium.

Step 8: The Insurer Calculates the Final Premium

After reviewing the records, the insurer recalculates the policy premium.

A simplified calculation is:

Actual payroll ÷ 100 × class rate = manual premium

The insurer then applies other policy factors. These may include:

Experience modifier
Schedule credits or debits
Premium discounts
State assessments
Policy fees
Minimum premium
Applicable endorsements

The final audit compares this amount with the premium already charged.

Example of a Workers’ Comp Audit

Assume an electrical contractor bought a policy using these estimates:

Estimated exposure	Amount
Field payroll	$300,000
Office payroll	$50,000
Uninsured subcontractor labor	$0

At the audit, the insurer finds:

Actual exposure	Amount
Field payroll	$360,000
Office payroll	$45,000
Uninsured subcontractor labor	$40,000

The insurer may add the extra field payroll and qualifying subcontractor exposure.

The office payroll reduction may create a small credit. However, the overall result will probably be an additional premium.

This example is hypothetical. Actual rates and audit rules vary by state and insurer.

What Are the Possible Audit Results?

A final audit usually produces one of three results.

Additional Premium

The contractor owes more money.

Common reasons include:

Payroll exceeded the estimate
New employees were added
Workers moved into higher-rated classifications
Owners were included
Subcontractors lacked proof of coverage
Work expanded into another state or trade

Return Premium

The insurer owes a refund or policy credit.

This may happen when:

Payroll was lower than estimated
Employees left during the year
Work was canceled
The contractor provided valid subcontractor certificates
A classification correction reduced exposure

No Significant Change

The original estimate was close to the actual exposure.

The contractor may receive a final statement with little or no balance.

What Is an Estimated Audit?

An estimated audit occurs when the insurer does not receive enough information to calculate actual exposure.

This may happen when the contractor:

Misses an appointment
Ignores audit requests
Submits incomplete records
Cannot provide payroll reports
Fails to answer follow-up questions

NYSIF explains that missed appointments, insufficient records, or no response can lead to an estimated payroll verification.

An estimated audit is often unfavorable because the insurer must account for uncertain exposure. The contractor may need to provide complete records before the insurer revises it.

California also warns that failure to cooperate can lead to cancellation, nonrenewal, collection action, and a substantial audit premium under its rules.

How to Review the Audit Report

Do not review only the final balance.

Compare:

Total payroll
Payroll by employee
Class codes
Rates
Owner payroll
Subcontractor charges
Experience modifier
Policy credits
Fees and assessments
Premium already paid

Look for simple errors first.

For example:

Did the auditor use the correct policy dates?
Was the same payroll counted twice?
Did the auditor overlook a subcontractor certificate?
Was an office employee classified as field labor?
Was an excluded owner added?
Did the insurer use the correct state?

Request the audit worksheet if the calculations are unclear.

How to Dispute a Workers’ Comp Audit

Start with the insurer or audit department.

Send a written explanation and supporting records. Clearly identify each amount or classification being disputed.

NCCI advises policyholders to attempt resolution with the carrier, pay undisputed premium, and provide a written explanation of the disputed calculation.

A dispute package may include:

Audit worksheet
Payroll reports
Timecards
Employee job descriptions
Subcontractor certificates
Contracts
Tax reports
Owner exclusion endorsements
Corrected calculations

If the dispute involves NCCI manual rules, eligible policyholders in many NCCI states may use NCCI’s dispute resolution process after attempting to resolve the issue with the insurer.

State appeal options vary. California, for example, provides regulatory resources for premium, audit, classification, and experience-rating disputes.

How Contractors Can Prepare for an Audit

Good preparation begins when the policy starts.

Track Payroll by Employee and Job

Keep accurate payroll and time records throughout the year.

Review Class Codes Early

Confirm each employee’s duties and classification before accepting the policy.

Collect Subcontractor Certificates Before Work

Do not wait until the audit. Track every expiration date.

Record Changes During the Year

Tell the insurer when the business adds employees, enters a new trade, or expands into another state.

Keep Owner Documents

Save exclusion forms, endorsements, ownership records, and exemption certificates.

Compare Estimates With Actual Payroll

Review payroll quarterly. Ask the agent to update estimates after a major change.

California notes that reporting large payroll changes during the policy term can reduce large audit bills or refunds.

Workers’ Compensation Audit Checklist

Before submitting the audit, confirm that you have:

Payroll registers for the full policy period
Quarterly federal and state tax reports
W-2, W-3, 1099, and 1096 records
Employee timecards
Employee job descriptions
General ledger and cash disbursement records
Subcontractor agreements
Workers’ compensation certificates
Owner exemption or inclusion documents
Records of work performed in other states
A copy of the original policy estimates
An explanation for unusual transactions

Organized records make the audit faster and easier to verify.

Frequently Asked Questions

Is every workers’ compensation policy audited?

Many policies are subject to a final audit. The exact audit method and requirements depend on the insurer, policy, and state rules.

How long does an audit take?

The time varies. A small remote audit may be completed quickly, while a contractor with many employees and subcontractors may require more review.

Can an audit increase my premium?

Yes. Higher payroll, class-code changes, owners, and uninsured subcontractors can increase the final premium.

Can I receive a refund?

Yes. Lower actual exposure may produce a refund or account credit.

Are 1099 payments reviewed?

Yes. The auditor may review 1099 forms, contracts, and invoices to determine whether payments involved subcontractors or possible employees.

Does a certificate automatically remove a subcontractor charge?

Not always. The certificate must usually match the business, work dates, and coverage requirements.

What happens if I ignore the audit?

The insurer may estimate the exposure. It may also pursue collection or take other action allowed by the policy and state law.

Can I challenge the final audit?

Usually, yes. Start with the insurer and submit a written dispute with supporting records.

Conclusion

A workers’ compensation audit converts estimated payroll and business exposure into a final policy premium.

The insurer reviews payroll, class codes, owners, and subcontractors. It may also examine contracts, tax reports, timecards, and accounting records.

Contractors face the greatest audit problems when records are incomplete. Uninsured subcontractors and incorrect classifications can also create large additional bills.

Keep accurate records throughout the policy year. Collect subcontractor certificates before work begins, and update the insurer after major payroll changes.

Finally, review the audit worksheet carefully. A contractor should understand every payroll amount, classification, and subcontractor charge before paying the final bill.

Editorial review: This guide was researched and reviewed by the Coverage Editorial Team using government agencies, insurance regulators, licensing authorities, policy documentation, and current industry pricing sources.