NCCI publishes the classification codes, the rules governing how payroll is assigned to them, and the experience rating plan used to calculate modifiers. It also produces the annual State of the Line report on the financial condition of the line.
Several states operate independent bureaus instead, each with its own classification system and rules. A business operating across state lines can find the same work classified differently in each.
Why it matters at audit
Audit rules are not universal. The manual that governs an audit depends on the state, which is why questions about specific limits and exclusions have to be answered per jurisdiction.