How to Handle a Workers' Comp Audit as a General Contractor

TL;DR: A workers' comp audit reconciles the payroll you estimated against actual numbers, and any subcontractor without their own WC certificate gets folded into your payroll at their classification rate. A $200,000 uninsured roofing sub can add $30,000-$80,000 to your premium, so collect a current WC certificate from every sub before work starts.

Your workers' comp carrier will audit you. It's not a question of if. Every policy includes a premium audit provision, and for general contractors, it's one of the most consequential financial events of the year. A clean audit confirms what you owe. A messy one hands you a bill that can be five or six figures more than you expected.

The difference between clean and messy is almost always the same thing: subcontractor documentation. This post covers what a workers' comp audit actually is, what the auditor is looking for, how your subs' records directly affect your premium, and exactly how to prepare so there are no surprises.

What a Workers' Comp Audit Is (and Why It Exists)

When you buy a workers' comp policy, the premium you pay upfront is an estimate. It's based on your projected payroll, your classification codes, and your experience modification rate (EMR). The carrier takes your word for it at the start of the policy period.

At the end of the policy period (usually 12 months), the carrier sends an auditor to verify the actual numbers. They compare what you estimated against what actually happened: your real payroll, your real classification of workers, and your real subcontractor usage. The difference between the estimate and reality determines whether you owe additional premium or get a refund.

For GCs, this audit is more complicated than it is for most businesses, because a significant portion of your labor force isn't on your payroll. It's on your subs' payrolls. And that distinction is where things get expensive if you don't have the right documentation.

The Subcontractor Problem: Why Your Subs' Insurance Is Your Problem

Here's the rule that catches most GCs off guard the first time:

If a subcontractor working on your project does not have their own workers' comp coverage, your carrier will include that sub's labor cost in your payroll calculation for premium purposes.

Read that again. If your drywall sub has a $200,000 contract and no workers' comp policy, your carrier will treat that $200,000 as if it were your payroll. Your premium gets recalculated with that amount added to your payroll base, at whatever classification rate applies to the sub's work.

For high-risk trades (roofing, demolition, structural steel), the classification rates can be $15 to $40+ per $100 of payroll. A $200,000 uninsured roofing sub could add $30,000 to $80,000 to your workers' comp premium. For one sub. On one project.

This is not a penalty. It's how the system works. The carrier's logic is straightforward: someone is performing labor on your behalf, and if they're not insured for workplace injuries, the risk falls on you. Your policy absorbs that risk, and you pay for it.

What the Auditor Will Ask For

Workers' comp auditors are methodical. They follow a standard checklist, and for GCs, the subcontractor documentation section is the most scrutinized part. Here's what they'll request:

1. Your Payroll Records

Total payroll by classification code for the audit period. This includes wages, salaries, bonuses, commissions, overtime (at straight-time value in most states), and the value of certain benefits. The auditor will reconcile this against your tax filings (941s, state unemployment reports) to make sure the numbers match.

2. Your Complete List of Subcontractors

Every sub who performed work during the policy period. Name, contract amount, scope of work. The auditor wants to account for every dollar of labor performed on your behalf, whether by your employees or someone else's.

3. Certificates of Insurance for Every Sub

This is the big one. For each sub on your list, the auditor needs proof that the sub carried their own workers' comp policy during the time they worked on your projects. A current COI is not sufficient. The coverage dates on the certificate must overlap with the dates the sub actually performed work.

If you can't produce a COI for a sub, or if the COI dates don't cover the work period, the auditor will include that sub's contract value in your payroll.

4. Subcontractor Agreements

Some auditors will request copies of your subcontract agreements to verify the scope of work and confirm the relationship is genuinely a subcontractor arrangement (not an employee misclassified as a sub). If the auditor determines a "sub" is actually functioning as an employee, their entire compensation gets added to your payroll regardless of their insurance status.

5. 1099s Issued

The auditor cross-references your 1099-NEC filings against your sub list. If you issued a 1099 to someone who isn't on your sub list with a matching COI, that's a red flag. It means you paid someone for labor and can't document their insurance status.

6. Material vs. Labor Breakdown

For subs who provide both materials and labor (common in trades like electrical, plumbing, HVAC), the auditor may allow you to exclude the material portion from the premium calculation. But only if you can document the split. If the subcontract is a single lump-sum number with no material/labor breakdown, the auditor will typically treat the entire amount as labor.

This is worth getting right at contract time. A $150,000 HVAC subcontract where $60,000 is equipment and $90,000 is labor should be documented as such in the subcontract or purchase order. Without that documentation, you'll pay premium on the full $150,000.

The Five Most Expensive Audit Mistakes

Mistake 1: Not Collecting COIs Before Work Starts

The most common and most expensive mistake. The sub starts work, you plan to "get the paperwork later," and later never comes. By the time the audit rolls around, the sub has finished, been paid, and has no incentive to dig up old certificates.

Prevention: No COI on file, no work starts. Period. This is the single most important compliance discipline for controlling your workers' comp premium.

Mistake 2: Having COIs That Don't Cover the Work Period

You have a COI for the sub, but it's dated January through December 2025, and the sub worked on your project in February 2026. The COI proves the sub had insurance last year. It proves nothing about this year. The auditor will flag it, and the sub's contract value goes into your payroll.

Prevention: Track expiration dates and collect renewed COIs before the old ones expire. If a sub is working across policy periods, you need certificates covering both periods.

Mistake 3: Missing the Sole Proprietor Exception

In most states, sole proprietors and partners are exempt from the requirement to carry workers' comp for themselves (though they must cover any employees they have). If an auditor includes a sole proprietor's contract in your payroll and the sub had no employees, you may be able to contest it.

But you need documentation: a signed exclusion form, proof of sole proprietor status (W-9 showing individual or sole prop classification), and confirmation that the sub had no employees during the work period. Without that documentation, the auditor defaults to including the contract value.

Mistake 4: Ignoring the Material/Labor Split

As discussed above, failing to document material costs separately from labor costs means the auditor treats everything as labor. On a $300,000 mechanical subcontract where $120,000 is equipment, that's $120,000 of unnecessary premium base. At a $10 per $100 rate, that's $12,000 in avoidable premium.

Prevention: Structure subcontracts with separate line items for materials and labor. If the sub provides a lump-sum bid, ask them to break it out. Get the split documented before work starts, not after the audit letter arrives.

Mistake 5: Misclassifying Employees as Subcontractors

If someone works exclusively for you, uses your tools, follows your schedule, and you control how the work is done, they're probably an employee regardless of what you call them. Auditors are trained to spot this, and the consequences go beyond workers' comp: you're also looking at tax liability, unemployment insurance, and potential penalties from the IRS and state labor agencies.

This isn't a paperwork fix. If the working relationship looks like employment, the solution is to put the person on your payroll, not to create a subcontract that says otherwise.

How to Prepare: The 30-Day Audit Prep Checklist

Your audit notification typically arrives 30 to 60 days before the audit date. Here's what to do when the letter shows up.

Week 1: Gather Your Sub Records

Pull every subcontractor agreement, COI, and payment record for the audit period. Create a master list: sub name, contract amount, work dates, COI on file (yes/no), COI coverage dates, WC policy confirmed (yes/no).

If you're using a spreadsheet for this, now is when you'll feel the pain. Every missing document is a phone call, an email chain, and a wait. If you're using a compliance management tool like PaperBoss, this is a report you can pull in minutes, because every COI, expiration date, and coverage verification is already tracked and stored.

Week 2: Fill the Gaps

For every sub where you're missing a COI or the dates don't match, contact the sub or their insurance producer directly. Request a certificate showing coverage during the specific dates they worked on your projects. Be precise: "I need a COI showing active WC coverage from March 15 to September 30, 2026" is much more effective than "send me your insurance info."

Some subs will have changed carriers during the period. You may need two certificates for the same sub. That's fine. Get both.

For subs who are sole proprietors with no employees, get a signed exemption letter and a copy of their W-9. Check your state's rules on sole proprietor exemptions, as they vary.

Week 3: Reconcile Your Numbers

Compare your sub list against your 1099 filings. Every 1099 recipient should either appear on your sub list with a matching COI or have an explanation (material supplier, equipment rental, professional services not requiring WC). The auditor will do this comparison, so do it first and resolve any discrepancies.

Review your payroll records for accuracy. Make sure classification codes are correct. A framing carpenter classified under a general carpentry code might seem minor, but classification codes have different rates, and the wrong code in the wrong direction costs you money.

Week 4: Organize and Stage

Create a clean audit package: payroll summary by classification, sub list with COI status, copies of all COIs organized by sub, 1099 summary, and any supporting documentation (sole proprietor exemptions, material/labor breakdowns). Have it ready before the auditor arrives.

Being organized signals to the auditor that you take compliance seriously. It also makes the audit go faster, which is better for everyone.

During the Audit: What to Expect

Most audits are conducted on-site or virtually and take 2 to 4 hours for a mid-size GC. The auditor will:

1. Review your payroll records and compare them to tax filings
2. Go through your sub list and match each sub to a COI
3. Flag any subs without adequate documentation
4. Ask questions about sole proprietors, material splits, and classification codes
5. Calculate the actual premium based on verified numbers
6. Provide a preliminary summary (the final bill comes later from the carrier)

You have the right to be present, ask questions, and provide additional documentation. If the auditor flags a sub and you have additional records that weren't in your initial package, provide them. Auditors aren't adversarial. They're verifying numbers. If you can prove coverage, they'll adjust.

After the Audit: Disputing the Results

If the audit produces a bill you believe is incorrect, you can dispute it. Common grounds for dispute:

• COI obtained after the audit: If you subsequently obtain a certificate proving a sub had coverage during the work period, submit it to the carrier. Most carriers will re-run the calculation.
• Incorrect classification codes: If the auditor assigned a higher-rate code to work that should be classified differently, provide evidence (subcontract scope, job descriptions) supporting the correct classification.
• Material/labor split documentation: If you can provide invoices, purchase orders, or subcontract amendments showing the material portion of a contract, the carrier may adjust.
• Sole proprietor exemption: If an auditor included a sole proprietor's contract and your state exempts sole props, provide the documentation.

File disputes in writing within 30 days of receiving the audit results. Include all supporting documentation with your dispute letter.

The Long Game: Building an Audit-Proof System

Surviving one audit is manageable. Building a system that makes every audit clean is what separates GCs who grow from GCs who get crushed by overhead.

The fundamentals:

Collect before work starts. Every sub provides a COI with active WC coverage before they set foot on your jobsite. No exceptions, no "I'll get it to you Monday," no starting work on a handshake.

Track expirations actively. A COI collected at onboarding expires 12 months later. If the sub is still working for you, you need a renewal. Automated expiration tracking, whether through PaperBoss or whatever system you use, prevents the mid-project lapse that becomes an audit problem.

Document material/labor splits upfront. Build it into your subcontract template. A single line item that separates materials from labor saves you money at every audit for the life of your business.

Keep everything in one place. When the audit letter arrives, you should be able to produce your complete sub documentation in under an hour. If it takes you a week of digging through email, shared drives, and filing cabinets, your system is costing you money.

Reconcile quarterly. Don't wait for the audit to find out you have gaps. Run your own internal check every quarter: which subs are active, which COIs are current, which ones are expiring in the next 60 days. Fix gaps while you still have leverage (the sub is still working for you and wants to keep getting paid).

The Bottom Line

A workers' comp audit is not something that happens to you. It's something you prepare for all year long by maintaining clean subcontractor records. The GCs who get hit with surprise five-figure audit bills are almost always the ones who let documentation slide during the year and scrambled to assemble records after the audit notice arrived.

The GCs who breeze through audits are the ones who treat subcontractor compliance as an ongoing discipline, not an annual fire drill.

If you're managing sub compliance in spreadsheets and email, an audit is the moment that system breaks down. If you want a system that keeps your COIs, W-9s, and workers' comp certificates organized, tracked, and audit-ready year-round, PaperBoss was built for exactly this. Start a free trial and see what audit-ready actually looks like.