Workers Comp Mod Rate Prep Fall Audit

Why this matters

The experience modification factor (Ex Mod, or X-Mod) is the multiplier applied to your workers compensation base premium that reflects your loss history versus the industry average for your classification codes. Per the NCCI Experience Rating Plan Manual, the calculation uses three years of payroll and loss data ending one year before the rating effective date. Most carriers compute the mod from data submitted during the year-end audit. That audit, which most trade businesses experience as a phone call or web form in September through January, is the single most consequential 30 minutes for your insurance cost in the following year. Going in prepared can move the needle materially. This SOP is documentation guidance and audit prep only - it is not legal advice and it is not state-specific reimbursement strategy. Consult your licensed agent or attorney for jurisdiction-specific issues.

Pre-audit document gather (4 weeks before)

Pull these documents into a single dated folder:

• Payroll register by employee for the full audit period (12 months matching the policy term)
• Form 941 quarterly returns for each quarter in the audit period (reconcile to payroll register)
• W-2 and W-3 from the audit period for officer-comp verification
• Subcontractor list with name, EIN, scope of work, and dates engaged
• Subcontractor Certificates of Insurance (workers comp AND general liability) showing coverage in force on all dates the sub was engaged
• 1099-NEC and 1099-MISC summary for the audit period
• Job descriptions for each employee on payroll
• Time records or job-cost system showing employee hours by job type if you use multiple class codes

The COI gather is where most audits add unexpected premium. ANY subcontractor without a current COI on file is reclassified as an uninsured employee for premium purposes per the NCCI Basic Manual rules followed by most states.

Reconcile payroll to ANY external source

The auditor will cross-check at least one of:

• 941 quarterly wages reported to IRS
• State unemployment insurance (SUI) quarterly wage reports
• W-3 transmittal totals for calendar-year coverage

Pre-audit, reconcile your payroll register to the 941s on a quarter-by-quarter basis. Discrepancies are the most common source of post-audit adjustments. Common causes of mismatch:

• Bonus checks issued outside the regular payroll run
• 401(k) elective deferrals included in some totals but not others
• Section 125 cafeteria-plan deductions causing taxable-vs-gross differences
• Reimbursements paid as taxable rather than non-taxable
• Mid-year employee classification changes

Document every reconciling item BEFORE the auditor finds it.

Class code review

Per the NCCI Scopes Manual, each employee is assigned a class code based on their PRIMARY duties. Misclassification can result in either over-premium (classifying a clerical worker as a roofer) or under-premium followed by an audit-driven additional bill (classifying a roofer as office). Both are problems; carriers are more aggressive about under-classification.

Common trade class code splits:

• Office-clerical (NCCI 8810 in most NCCI states) - lower rate, but employee must perform exclusively clerical duties and have no exposure to operational areas other than transit
• Outside sales (NCCI 8742) - sales personnel away from premises
• HVAC installation (NCCI 5183 in most NCCI states) - field installation
• Plumbing (NCCI 5183 also, in most NCCI states)
• Electrical wiring inside (NCCI 5190)
• Carpentry residential (NCCI 5645)
• Roofing (NCCI 5551) - typically the highest-rate class for residential trades
• Drivers (NCCI 7380) - commercial drivers separate

Working owner-officer comp follows separate state-specific minimums and maximums per the NCCI manual; some states cap owner payroll at a fixed limit regardless of actual draw.

Run through your roster line by line; verify each person's class code matches actual primary duties. Document any split-class employees (some payroll attributed to office, some to field) with time-record support; without records, the auditor will assign the highest-rate class to the full payroll for that employee per the NCCI rules.

Subcontractor file scrub

Per the NCCI Basic Manual and almost every state's rule:

• If the subcontractor has workers comp coverage in force during their engagement and the COI documents it, the sub's payroll is NOT added to your premium.
• If the subcontractor does NOT have workers comp coverage in force, OR you cannot produce the COI to the auditor, the sub's payroll IS added to your premium at the appropriate class rate.

What the COI must show:

• Subcontractor name matching the name on your records
• Policy number
• Policy effective and expiration dates that bracket the engagement
• Workers comp coverage in Section A of the Acord 25 or equivalent
• Cancellation notice provision (many carriers require this)

For each subcontractor:

• Pull every check you issued
• Match each check date to a COI showing coverage in force on that date
• Identify gaps and chase the subcontractor for back-dated COI evidence BEFORE the auditor arrives
• Document any sub who is a sole proprietor exempt from workers comp under state law (most states allow this; the auditor will want the exemption certificate)

Experience modification basics (terminology only)

The NCCI Experience Rating Plan Manual defines:

• Eligibility threshold - states publish payroll or premium minimums for experience rating; below the threshold the mod is 1.00 by definition
• Expected losses - calculated from your payroll by class code multiplied by the state-specific expected loss rate per class
• Actual losses - claims paid plus reserves during the experience period
• Primary loss - the portion of each claim up to a state split point (in most NCCI states $18,500 in 2025) that fully impacts the mod
• Excess loss - the portion above the split point, weighted down in the calculation
• Ballast and weighting values - actuarial modifiers from the manual

A mod below 1.00 produces a credit (premium reduction); a mod above 1.00 produces a debit (premium increase). The exact mathematics is published in the Plan Manual and verified by the rating bureau (NCCI in most states; California has its own WCIRB, New York NYCIRB, Pennsylvania PCRB, others).

What you can legitimately do BEFORE audit

References

• NCCI Experience Rating Plan Manual (state-specific edition)
• NCCI Basic Manual for Workers Compensation and Employers Liability Insurance
• NCCI Scopes of Basic Manual Classifications
• IRS Form 941 (Employer Quarterly Federal Tax Return)
• State workers compensation rating bureau (NCCI in 38 jurisdictions; WCIRB California; NYCIRB New York; PCRB Pennsylvania; others)
• Acord Form 25 Certificate of Liability Insurance standard