The experience modifier is a numerical multiplier applied to your workers’ comp premium based on your three-year claims history compared to the industry average for your class codes. A mod of 1.00 means average; below 1.00 is a credit (you pay less); above 1.00 is a debit (you pay more). The mod is calculated by the National Council on Compensation Insurance (NCCI) for most states or by state rating bureaus (Maryland has its own). A swing from a 1.20 mod to a 0.85 mod represents roughly a 30% premium difference on the same payroll — making mod management one of the highest-ROI activities in workers’ comp. We audit mod calculations annually and challenge errors when warranted.