Why are work comp policies audited?

The NC workers compensation policy is rated based on your payroll. Since no one can know the exact payroll that you will have in the coming 12 months, the insurance company asks you for an estimate. After those 12 months are over, the insurance company will audit your actual payroll figures and adjust your final rate to reflect this payroll. This can generate either an additional premium due, or a refund due you or no change at all.