How Are Workers’ Comp Premiums Calculated? Class Codes, Payroll, and Your Mod

Unlike most insurance, workers’ compensation pricing is not a black box – it is a published formula. Contractors who understand the formula can influence nearly every variable in it. Here is the whole calculation, demystified.

The Basic Formula

(Payroll ÷ 100) × Class Code Rate × Experience Mod = Premium

Three inputs. Let’s take them one at a time.

Input One: Classification Codes

Every type of work carries a class code, and every code carries a rate reflecting the historical injury costs of that work. Clerical staff might rate under $1 per $100 of payroll; carpentry might run mid-single to low-double digits; roofing can exceed $20. Your operation may legitimately span several codes – and that is where money hides:

• Misclassification upward (your trim carpenter rated as a framer) silently overcharges you all year.
• Misclassification downward gets corrected at audit with a bill you did not budget.
• Payroll separation matters: if records clearly separate office, sales, and field payroll, each is rated at its own code. Vague records get everything lumped at the highest applicable rate.

Input Two: Payroll

Premium scales with payroll, but “payroll” has rules: overtime is often rated at straight-time equivalents (if your records show it), owner compensation may be capped or subject to elections, and payments to uninsured subcontractors typically get added as if they were payroll. Clean books directly reduce premium; messy books are rated against you.

Input Three: The Experience Mod

The experience modification factor compares your actual losses to what is expected for businesses your size in your codes. A mod of 1.0 is average; 0.85 means 15% credit; 1.30 means a 30% surcharge. Two things every contractor should know about mods:

1. Frequency hurts more than severity. The formula weighs the number of claims heavily – five $4,000 claims damage your mod more than one $20,000 claim. Return-to-work programs and small-claim management protect the mod.
2. Your mod is a bidding credential. Many GCs and project owners screen subs by mod, sometimes refusing anyone above 1.0. Your mod is not just a pricing factor – it is a marketing document.

Then Comes the Audit

Comp premiums are provisional – based on estimated payroll. After the policy year, the carrier audits actual payroll and settles up. Contractors who underestimated get a bill; overestimators get money back. Audit survival kit: accurate quarterly payroll records, overtime broken out, certificates from every sub, and job descriptions that support your class codes.

Five Ways to Pay Less, Legitimately

• Verify every class code on the policy annually.
• Separate payroll by duty in your accounting system.
• Collect sub certificates religiously.
• Report claims fast and bring injured workers back on light duty – open, drifting claims inflate the mod.
• Review your mod worksheet for errors; they are more common than you would hope.

Reading Your Mod Worksheet: A Five-Minute Audit

Once a year, request your experience rating worksheet and check four things: that listed payrolls match your records by class code, that every claim shown is actually yours and closed claims show final (not inflated reserve) values, that clerical errors have not merged another company’s data into yours (it happens with similar names), and that the anniversary rating date aligns with your policy. Errors in mod calculations are corrected through your carrier or the rating bureau – and because the mod multiplies your entire comp premium, a correction pays for the five minutes many times over.

Frequently Asked Questions About Comp Premium Calculation

What payroll counts for owners and officers?

States assign fixed or capped payroll figures for owners who elect coverage, regardless of actual draws. Electing in or out changes both premium and protection – revisit the election whenever ownership or income changes.

Does overtime premium pay increase my comp premium?

The overtime excess (the half in time-and-a-half) is typically deductible from rated payroll – but only when payroll records break it out. Lumped payroll gets rated in full; itemized records save real money.

How long do claims stay on my mod?

The standard experience window covers three completed policy years, excluding the most recent. A bad year therefore haunts pricing for several renewals – and then rolls off, which is worth remembering when a rough mod feels permanent.

Why does my small business have no mod at all?

Experience rating starts at premium eligibility thresholds; smaller operations are rated without a mod until they qualify. Growth brings the mod – and with it, the return on safety investment compounds.

Can I estimate my premium before hiring my first employee?

Yes – class rate times projected payroll gets you close, and an agent can firm it up in minutes. Pricing coverage before the hire keeps labor decisions honest about their full cost.

My Policy Plug reviews class codes, mods, and audit results for Nevada contractors – often finding real money. Call 702-444-2367 for a comp checkup.