*5 min read · Last updated May 25, 2026*
In this article
– How workers’ comp class codes work – Where construction trades most often get misclassified – How the year-end audit catches it – What to do this week before your next audit – FAQ
Marcus Coleman runs a 7-person residential roofing crew in Phoenix. When his broker set up the workers’ comp policy in 2024, the entire payroll was booked under NCCI class code 5403, residential carpentry. The crew framed almost nothing. They tore off and replaced asphalt shingle roofs on 60 to 80 homes a year. At year-end the carrier’s auditor reviewed the certificates of insurance Marcus had issued to general contractors and the OSHA logs from a fall in October. The classification got corrected to 5551, residential roofing. The back-premium bill came to $42,300, and ate every dollar he had budgeted for new equipment in 2026.
How workers’ comp class codes work
Workers’ compensation premiums in most states are governed by the National Council on Compensation Insurance (NCCI), which publishes roughly 600 occupational class codes. Each code carries a base rate per $100 of payroll that reflects how often workers in that classification get hurt and how expensive their injuries tend to be.
Residential carpentry (5403) typically prices out at $3 to $5 per $100 of payroll in most NCCI states. Residential roofing (5551) typically sits between $15 and $25 per $100, because falls and roofing-related back injuries dominate the loss data. The difference between paying $4 and paying $19 per $100 on a $300,000 payroll is the difference between a $12,000 premium and a $57,000 premium.
Four states (Ohio, North Dakota, Washington, Wyoming) run monopolistic state-funded workers’ comp programs with their own rate schedules instead of NCCI. The same misclassification risk applies. The state fund’s auditor decides at year-end which classification fits the work that was actually performed.
Where construction trades most often get misclassified
The pattern repeats across trades. A roofing crew gets booked under carpentry because the framing component looked dominant on the broker’s intake call. An HVAC technician doing rooftop unit installs gets booked under sheet metal work when the rooftop time should trigger the roofing code. A landscaping crew that installs fences runs payroll under residential landscaping (0042) when split-rail and chain-link work belongs under fence erection (6400). A general contractor pays the GC class code (5606) on supervisory payroll and owes concrete pouring (5221) on the labor hours where the GC actually held the trowel.
The broker who placed the policy typically takes the description the owner offered. The auditor at year-end has no such latitude. They review payroll records, job descriptions, OSHA logs, and the certificates of insurance issued to every general contractor the crew worked for. If the COIs describe “roofing” and the policy describes “carpentry,” the policy gets corrected retroactively to match the documented work.
How the year-end audit catches it
Every workers’ comp policy includes an audit clause. Within 60 days of the policy expiration date, the carrier sends a field auditor or pushes the owner to fill out an online audit form. They want payroll by class code, the count of subcontractors hired, and certificates of insurance for each sub. If a subcontractor’s COI is missing or expired, the carrier rolls that sub’s payroll into your direct payroll at whichever class code best fits the work the sub performed.
The audit can move either direction. If actual payroll was lower than estimated, or a higher-rate class wasn’t actually performed, you get a refund check. If actual payroll was higher or the work was riskier than the policy described, you get a back-premium invoice with payment due in roughly 30 days. The state guaranty association sits behind that invoice if the business does not pay, which means collection actions move quickly.
What to do this week before your next audit
Pull last year’s audit worksheet from your carrier; your broker has a copy. Compare the class codes assigned against the work the crew actually performed. If anything looks mismatched, flag it now, while you still have months of clean payroll records to support the right classification. If your business has ever had an employee describe their job to a workers’ comp claim adjuster, an OSHA investigator, or a general contractor’s insurance verifier, pull that record. Inconsistent job descriptions across documents are exactly what audits use to override the policy classification.
Two adjacent angles worth a read: what workers’ compensation insurance actually covers lays out the benefits side, how much business insurance coverage you really need shows where workers’ comp fits inside a broader SMB stack, and workers’ comp for HVAC subcontractors walks through the sheet-metal vs roofing classification dispute specifically.
Get small business and contractor policies quoted against the right NCCI class codes from the start, with brokers who walk audit clauses before binding.
Compare commercial coverage optionsA workers’ comp audit bill that arrives in the mail isn’t a quote, it’s a corrected invoice for the policy you already used. The only protection against a six-figure surprise is making sure the class codes on your declarations page match the work your crew actually performs, every payroll cycle, every year.
Frequently asked questions
Who decides which NCCI class code applies to my crew? The carrier’s underwriter assigns codes at binding based on the application, then the auditor reviews and corrects them at year-end based on payroll records, job descriptions, and certificates of insurance.
Can I dispute a class code reclassification after an audit? Yes. You can request a re-review with documentation showing the actual work performed. If the dispute stays unresolved, NCCI offers an Inspection and Test Audit process, and most states have a workers’ comp rating bureau that reviews disputes.
Does the rate per $100 of payroll change every year? Yes. NCCI files loss-cost updates annually in each state, and individual carriers apply their own loss-cost multipliers and experience modification factors on top. Your “$15 per $100” rate this year might be “$16.20 per $100” next year before your Emod even moves.
What happens to my premium if a subcontractor’s certificate of insurance is missing at audit time? The carrier rolls that sub’s payroll into your direct payroll at the class code that fits the work they performed. A $60,000 sub roofing payroll added to your direct payroll at the 5551 rate can mean thousands in additional back-premium.
Is the class code system the same in every state? No. Most states use NCCI codes and rates as a starting point. Four monopolistic states (Ohio, North Dakota, Washington, Wyoming) maintain their own rate schedules and classifications. California, New York, Pennsylvania, Delaware, New Jersey, and others use independent state rating bureaus instead of NCCI.
