What Is a Workers' Comp Class Code — and Why Does Michigan Use Its Own?

Think you're on the wrong code? Have us review your Michigan workers' comp classification →

A workers' comp class code is the four-digit number that tells an insurance carrier what kind of work your employees actually do — and it is the single largest variable in what your policy costs. Two Michigan businesses with identical payroll can pay wildly different premiums purely because one is coded as clerical and the other as roofing. What most business owners don't know is that Michigan doesn't use the national NCCI classification system that nearly every article on this topic assumes. Michigan runs its own. That matters when you're trying to look your code up or compare it to advice written for another state.

How a class code sets your premium

Workers' compensation premium is one of the few insurance calculations you can actually do on a napkin. The basic formula:

(Annual payroll ÷ 100) × class code rate × experience modification factor = manual premium

Everything else — schedule credits, carrier deviations, minimum premiums, expense constants — adjusts around the edges of that core. The rate is expressed as dollars per $100 of payroll, and it is assigned to the class code, not to your company. That's the whole point: the classification system exists so that businesses doing similarly hazardous work share a rate and a loss pool.

Which is why the code selection is so consequential. A clerical office code and a structural steel erection code can be separated by more than an order of magnitude in rate. Put the wrong payroll in the wrong bucket and the error compounds across every dollar of payroll, every year, until someone catches it.

Why Michigan is different: CAOM, not NCCI

Most states delegate workers' compensation classification, statistical collection, and experience rating to the National Council on Compensation Insurance (NCCI). Michigan does not. Michigan is an independent bureau state, and the Compensation Advisory Organization of Michigan — CAOM, headquartered in Livonia — serves as the state's advisory organization.

What CAOM does:

• Maintains Michigan's classification manual — the official list of class codes and the rules for applying them in this state.
• Publishes the statistical plan that carriers use to report Michigan loss and payroll data.
• Administers the Michigan Workers' Compensation Placement Facility, the assigned risk market of last resort, and publishes its rates and rating values.
• Provides a public class code lookup tool on caom.com, so you can search Michigan's actual codes rather than a national list.

The practical takeaway: if you look up your business on a generic national class code site and the number doesn't match what's on your Michigan policy, that isn't necessarily an error — you may be looking at the wrong manual. Verify against Michigan's own system.

How your class code gets assigned

Classification follows the business, not the individual job title. The governing principle in workers' compensation classification is that you're classified by the nature of the employer's overall operation, and then employees are assigned to codes based on the work they actually perform within it. A few rules that trip owners up:

• You usually get one governing class code that describes your primary operation, plus a small number of standard exceptions — most commonly clerical office employees, outside sales, and drivers — that can be split out at their own (much lower) rates.
• Splitting payroll requires clean records. To put an employee's payroll in the clerical code, that employee generally has to be exclusively clerical. An office manager who also loads trucks two afternoons a week typically goes entirely into the higher-rated code.
• Adding a new service can change your code. A landscaper who starts doing tree removal, or a remodeler who starts doing roofs, has changed the hazard of the operation. That should be disclosed at the time, not discovered later.
• Officers and owners have their own rules on inclusion, exclusion, and payroll caps, separate from the classification question.

What a wrong class code actually costs you

It cuts both ways, and both directions hurt.

Coded too high and you overpay every single year, often for years, without any indication anything is wrong. Nothing in your policy flags it. The premium simply looks like what workers' comp costs.

Coded too low and the correction arrives at the worst possible moment. Workers' comp policies are auditable — the carrier reconciles estimated payroll against actual payroll after the policy year, and the auditor reviews your classifications while they're at it. A reclassification found at audit is applied retroactively to the whole policy period, producing an audit bill that can run into five figures with no warning. If you've ever wondered what makes an audit go badly, this is usually it. (We wrote separately about what happens when you skip the audit entirely — that's a different and worse problem.)

The class code is also upstream of your experience modification factor. Your mod compares your actual losses to the losses expected for your classification at your payroll size. Wrong code, wrong expected losses, distorted mod — which then multiplies through every future year's premium. If you want the full picture on that, see our breakdown of how the Michigan experience mod works.

How to check your own classification

1. Pull your declarations page and find the classification schedule — it lists each code, its description, the estimated payroll assigned to it, and the rate.
2. Read the code descriptions, not just the numbers. Ask whether the description genuinely matches what your people do all day. Owners are frequently surprised.
3. Look for missing standard exceptions. If you have genuinely clerical staff and there's no clerical code on the policy, their payroll may be sitting in your governing code at many times the correct rate.
4. Flag any operational change since the policy was written — new services, new equipment, work at heights, delivery added.
5. Have an agent review it against Michigan's manual before the audit does it for you.

Frequently Asked Questions

What is a workers' comp class code?

It's a four-digit code that classifies a business by the hazard of the work its employees perform, and it determines the rate used to calculate your premium. Premium is roughly annual payroll divided by 100, multiplied by the class code's rate, multiplied by your experience modification factor. Because the rate attaches to the code rather than to your company, the code assignment is the single largest factor in what your workers' compensation policy costs.

Does Michigan use NCCI class codes?

No. Michigan is an independent bureau state. The Compensation Advisory Organization of Michigan (CAOM) is the state's advisory organization — it maintains Michigan's own classification manual and statistical plan and administers the Michigan Workers' Compensation Placement Facility, the assigned risk market. If you look up a code on a national NCCI-based list and it doesn't match your Michigan policy, check Michigan's own manual before assuming there's an error.

What happens if my workers' comp class code is wrong?

If you're coded too high, you quietly overpay every year with nothing on the policy to signal it. If you're coded too low, the correction typically surfaces at the annual premium audit and is applied retroactively to the entire policy period, producing an unexpected audit bill. A wrong code also distorts your experience modification factor, because the mod measures your losses against the losses expected for your classification — so the error carries into future years as well.

Can I put my office staff in a cheaper class code?

Yes, if they genuinely qualify. Clerical office employees, outside salespeople, and drivers are standard exceptions that can be split out of your governing class code at their own much lower rates. The catch is that the split generally requires the employee to work exclusively in that capacity — an office manager who also helps load trucks or works in the shop is normally assigned entirely to the higher-rated code. Clean payroll records are what make a split defensible at audit.

How do I find my Michigan workers' comp class code?

It's listed on the classification schedule of your workers' compensation declarations page, along with the estimated payroll and rate assigned to each code. CAOM also publishes a public class code lookup for Michigan's classification system at caom.com. If the description on your policy doesn't match what your employees actually do, that's worth having an agent review against Michigan's manual before your next audit.

The bottom line

The class code is the cheapest thing on a workers' comp policy to get right and one of the most expensive to get wrong — and because Michigan runs its own classification system through CAOM rather than NCCI, a lot of the guidance business owners find online doesn't apply here cleanly. Pull your declarations page and read the classification schedule. If the descriptions don't sound like your business, something is off. J. Jacobs & Associates represents 20+ commercial carriers and writes Michigan workers' comp every day, and reviewing a classification schedule costs you nothing. Send us your current workers' compensation declarations page or request a free comparison, and we'll tell you whether your codes are right before an auditor tells you they weren't.