ACC classification units, explained

Every levied business in New Zealand sits in a classification unit — a five-digit code that groups activities with similar injury risk. The unit sets the Work Account levy rate per $100 of liable earnings, and the differences are not small: office-work units sit around ten cents while roofing sits over two dollars.

How a unit is assigned

Your Business Industry Classification (BIC) code — chosen when you registered with IRD, often in thirty seconds, often years ago — maps to a CU. ACC bills whatever that mapping produces until told otherwise.

The rule when more than one description fits

ACC's guidebook is explicit: where several descriptions fit, the one with the highest levy rate applies; where several sit at that rate, the one carrying the largest share of liable earnings. Self-employed people always hold exactly one unit. Employers can hold more than one, but only by meeting all four of ACC's conditions for separate activities — most businesses do not.

Why classifications go stale

Businesses drift: the fabricator starts importing, the builder moves to design and project management, the workshop becomes a desk. The classification does not follow by itself — ACC reassesses when told, and the telling is a form most people have never heard of. Until then, yesterday's risk keeps setting today's levy.

Sources: ACC Levy Guidebook 2026-27; ACC — sort a levy problem.