A routine payroll audit for a small roofing contractor in Des Moines, Iowa, turned up something the owner never expected: his single employee roster had been assigned to three different workers compensation premium class codes. One employee who spent mornings in the office answering phones and afternoons on job sites was being charged at the clerical rate for part of his pay and the roofing rate for the rest. The sales representative who drove to client meetings was classified under a separate code for outside sales. The audit, conducted by an independent auditor from NCM Group, found that roughly 40 percent of the total payroll had been assigned to the wrong class. The result was a retroactive premium bill of $18,000, plus a revised experience modification factor that would raise costs for the next three years.

The Audit That Snagged a Roofer on Three Codes

The roofer in question had been in business for about seven years and carried a standard workers compensation policy through a regional carrier, Heartland Mutual. Each year, the carrier estimated the premium based on the owner's reported payroll split among class codes. The owner had always listed every employee under code 5551, which covers roofing—the highest-risk work his crew performed. But when the annual audit came, the insurer sent a field auditor to review payroll records, job descriptions, and time cards.

The auditor found that the owner had not separated payroll by actual duties. The office manager, who spent roughly 60 percent of her time on clerical tasks and 40 percent on light roofing support (handing materials, cleaning up), was coded entirely as roofing. The outside sales rep, who never touched a roof, was also coded as roofing. Under National Council on Compensation Insurance (NCCI) rules, clerical workers belong to code 8810, and outside sales personnel belong to code 8742. The auditor reclassified the payroll accordingly.

Because the roofing code carries a rate around $15 per $100 of payroll, while clerical and sales codes run closer to $0.50 per $100, the misclassification had artificially inflated the estimated premium by thousands of dollars. But the audit adjustment went both ways: the carrier refunded the overpaid premium on the misclassified clerical payroll and then billed the difference on the previously underreported roofing payroll. The net effect was an $18,000 additional premium, plus a penalty for late payment of the underpaid portion.

The owner later told the auditor that he had no idea workers comp class codes existed. He had assumed all his employees were in the same bucket because they all worked for his roofing company. That assumption is common among small contractors, and it is one of the most expensive mistakes a policyholder can make.

Why Premium Class Codes Are the Hidden Levers of Workers Comp

Workers compensation premium is not a flat rate per employee. Instead, each state's rating bureau or the NCCI publishes a set of class codes, each with a base rate that reflects the injury risk for that type of work. The base rate is multiplied by the employer's experience modification factor (mod) and then by the payroll in that class. A high-risk class like roofing (code 5551) may have a base rate of $15 per $100 of payroll, while clerical (code 8810) might be $0.50, and outside sales (code 8742) could be $0.75.

These rates are not arbitrary. They are derived from years of loss data: how many claims, how severe, for each occupation. Roofers fall off ladders, burn themselves with tar, and suffer repetitive-motion injuries. Clerical workers rarely file claims, and when they do, the costs are low. The class code system is designed to match premium to risk, so that a roofing company pays more than a law firm, even if both have the same total payroll.

But the system only works if employers accurately assign each employee's payroll to the correct code. When an employee performs multiple duties—say, an office worker who occasionally helps on a roof—the payroll must be split between the applicable codes based on the actual time spent in each activity. NCCI's Scopes manual provides detailed definitions and rules for each code, including which jobs are included and which are excluded.

For small business owners, the complexity is daunting. A single employee might legitimately work under two or three codes in a week. Without careful time tracking, the default is often to put everyone in the highest-risk code, which overpays premium, or in the lowest-risk code, which underpays and invites audit adjustments. The roofer in our example was doing the former, but the audit caught him on the latter for his sales staff.

The Payroll Audit: Where the Numbers Meet Reality

The annual payroll audit is the mechanism that reconciles the estimated premium paid at the start of the policy period with the actual premium based on real payroll. Carriers typically estimate premium using the prior year's payroll or the owner's projection. At the end of the policy year, an auditor—either an employee of the carrier or an independent firm—reviews the employer's payroll records, tax filings, and sometimes time cards or job logs.

The auditor looks at every dollar paid to employees: regular wages, overtime, bonuses, commissions, and even some fringe benefits like the value of lodging or meals if they are considered remuneration. For subcontractors, if the contractor does not have its own workers comp coverage, the subcontractor's payroll may be included in the hiring contractor's audit and charged at the appropriate class code. This is a common trap for roofing contractors who hire day laborers or uninsured subs.

The audit also checks that the class codes assigned to each employee match their actual duties. If an employee was coded as clerical but spent half the year on roofing, the auditor will reclassify that portion of payroll to the roofing code and bill the difference. If the employee was coded as roofing but actually did clerical work, the carrier owes a refund—but only if the employer can prove the clerical duties, which often requires time records.

In the roofer's case, the auditor spent two hours in the office, reviewed quarterly tax returns, and interviewed the owner about each employee's typical week. The office manager's time records showed she logged about 25 hours per week on administrative tasks and 10 hours on roofing support. The auditor split her payroll 60/40 between clerical and roofing codes. The sales rep had no time records but the owner confirmed he never performed physical work on roofs, so his entire payroll was moved to outside sales.

The final audit report showed a net increase in premium because the underreported roofing payroll for the office manager and the rep outweighed the overreported clerical payroll. The carrier issued a bill for $18,000, due within 30 days. The owner had to borrow from a business line of credit to pay it.

How Misclassification Happens—and Gets Caught

Misclassification of workers comp class codes is widespread. The NCCI has estimated that roughly 14 percent of payroll nationally is assigned to the wrong class code, with some industries—construction, trucking, and healthcare—having higher rates. The reasons range from simple ignorance to deliberate fraud. An employer who knows the rules might intentionally classify a roofer as a clerical worker to save thousands in premium. That is premium fraud, and state fraud bureaus actively pursue it.

But most misclassification is unintentional. Small business owners often do not know that class codes exist. They may rely on a general agent who sets up the policy with a single code for simplicity. Or they may think that because all employees work for the same company, they all belong in the same class. The NCCI's classification system, however, is based on the employee's individual duties, not the employer's industry.

State fraud bureaus and insurance carriers use data-mining to detect anomalies. For example, a roofing company with zero payroll in the roofing code and all payroll in clerical will trigger a red flag. Carriers also compare payroll reported to workers comp with payroll reported to the IRS and state unemployment agencies. Discrepancies can lead to an audit or investigation.

The roofer in our story was not trying to cheat. He simply did not know the rules. But the carrier's audit found the errors anyway. The cost to the business was not just the $18,000 but also a higher experience mod for the next three years, because the reclassified payroll increased the expected losses in the rating calculation. Higher mod means higher premium on every policy for years to come.

The Financial Ripple Effect of a Reclassification

The immediate impact of a reclassification is the retroactive premium bill. But the ripple effects can last much longer. The experience modification factor (mod) is calculated using a formula that includes the employer's actual losses compared to expected losses for their class codes. When an audit reclassifies payroll to higher-risk codes, the expected losses increase, which can lower the mod if the employer's actual losses are low relative to the new expected losses. But if the employer has had claims, the mod can rise, increasing premium for years.

In the roofer's case, the reclassification raised his expected loss basis significantly because the roofing code carries a higher expected claim frequency and severity. His actual claims were minimal—one minor sprain—so his mod actually dropped slightly after the reclassification. But the premium on the newly classified payroll was still higher because the base rate per $100 was much higher. His annual premium after the audit went from about $22,000 to $34,000.

Beyond the mod, the reclassification triggered a non-renewal notice from his carrier. The carrier's underwriting guidelines flagged any audit adjustment over $10,000 as a risk indicator. The owner had to shop for a new policy with a higher rate because his loss experience now looked riskier to other carriers. Some carriers specialize in high-risk contractors and might offer coverage, but at a premium that can be 50 percent higher than standard market.

For small businesses, these adjustments can be devastating. Thin margins mean that an unexpected $18,000 bill can wipe out a year's profit. The owner of the roofing company told the auditor that he would have to lay off one employee to cover the cost. He also started requiring all employees to fill out daily time sheets showing which tasks they performed, so that future audits would have clear documentation.

Tools to Keep Your Payroll Coding Clean

The best defense against a costly reclassification is proactive payroll management. Employers should review their class code assignments at least quarterly, especially if employees' duties change or new positions are created. NCCI's Scopes manual is the definitive reference for class code definitions and is available online through the NCCI website or state rating bureau portals. Some carriers also provide classification guides to their policyholders.

For employees who perform multiple duties, the employer must track the time spent in each activity. This can be done with simple paper logs, a spreadsheet, or time-tracking software that allows tagging tasks by class code. The key is consistency: the records need to be contemporaneous, not reconstructed after the fact. Auditors are trained to spot reconstructed records that look too neat or lack detail.

However, there is a trade-off. For a small business with a handful of employees, requiring daily time sheets for every task can feel like overkill. The office manager who sometimes hands a shingle up a ladder may resent filling out a form for a five-minute task. And if the employer over-classifies everyone into the highest-risk code just to avoid the tracking hassle, they end up overpaying premium—but at least they avoid audit surprises. Some owners deliberately choose this path, accepting the higher premium as the cost of simplicity. It is a legitimate strategy, but it means leaving money on the table year after year. The roofer in our story, before his audit, was actually overpaying for his sales rep and office manager by coding them as roofing, while underpaying for the roofing labor. The net result was a bill, but if he had coded everyone as clerical, he would have underpaid even more and faced a larger adjustment. Over-classification to the highest risk code usually results in a refund, but the employer still loses the use of that money during the policy year.

Consulting a licensed insurance agent who specializes in workers comp is another essential step. An experienced agent can review the employer's operations and recommend the correct class codes before the policy is issued. They can also advise on whether to use a single code for an employee who primarily does one job but occasionally performs another. In some cases, the NCCI allows a "governing class" if the secondary duties are incidental (less than 10 percent of time). But the rules vary by state and code.

Finally, employers should conduct an internal audit before the carrier's auditor arrives. Compare payroll records with class codes, verify that subcontractors have their own coverage, and gather time records for any employees with split duties. A self-audit can catch errors early and allow the employer to correct them on the next renewal, avoiding a retroactive bill. Some carriers offer a voluntary disclosure program where employers can report misclassifications without penalty, but only if the error is discovered before the carrier's audit.

The roofer in our story now runs a quarterly payroll review and has separate time codes for each employee's function. He also switched to a payroll service that integrates with his workers comp policy, automatically splitting payroll by class code. His premium has stabilized, but he still pays more than he did before the reclassification, and he expects the experience mod to keep his rates elevated for at least three more years. The lesson is clear: ignorance of the class code system is not a defense, and a few hours of upfront attention can save thousands in retrospective adjustments.

This article is for informational purposes only and does not constitute professional insurance advice. Employers should consult a licensed agent or attorney for guidance specific to their situation.