A classification unit (CU) is the five-digit code ACC uses to set your Work levy rate. Every business and self-employed person has one, based on their BIC code and the work they do. It’s printed on your invoice next to the rate — for example “CU 42420 Carpentry services”, $1.76 per $100 in 2026/27.
When you file a tax return or register for GST you choose a Business Industry Classification (BIC) code describing what you do — ACC’s example is E323120 Gas plumbing. Inland Revenue passes it to ACC along with your income, and ACC uses it to assign your CU. Several BIC codes can lead to the same CU: plumbing services has seven.
The guidebook’s test for choosing is the activity: for a business, the service it provides or the product it makes or sells — administration, marketing and similar support work count as part of that, not as separate activities. For a self-employed person, it’s the nature of the work you do, not the business you do it in. Generic words like “consultant” or “investment” don’t describe an activity. You can search codes at businessdescription.co.nz.
Sources: ACC — Understanding your levy invoice (last published 16 September 2025, checked 30 September 2026); ACC Levy Guidebook 2026/27 (checked 30 September 2026)
ACC groups CUs into levy risk groups by how often injuries happen, how severe they are and how long people take to get back to work, and sets the rates from past claims. In 2026/27 the Work levy runs from $0.02 to $5.29 per $100. Carpentry (42420) is $1.76; office administrative services (78540) is $0.21. On $100,000 of income, that gap is $1,550 a year.
Sources: ACC Levy Guidebook 2026/27 (checked 30 September 2026); ACC — Understanding your levy invoice (last published 16 September 2025, checked 30 September 2026); ACC Levy Guidebooks 2022/23 to 2026/27, levy rate tables (cross-checked against the schedules of the Work Account Levies Regulations 2022 and 2025 — 8,055 figures, no differences, checked 25 September 2026)
Source: ACC Levy Guidebook 2026/27 (checked 30 September 2026)
Check the CU ACC holds in MyACC for Business, and your BIC code at businessdescription.co.nz. If it doesn’t describe what you do, contact ACC’s business team — 0800 222 776 or business@acc.co.nz — with your name, ACC number and what you’d like looked at. Update the BIC code in both MyIR and MyACC for Business, so next year’s filing carries the right one.
ACC decides whether a change applies and from when. If you disagree with its decision, you can apply for an independent review within three months of it.
In the one case we’ve followed through to the end, ACC moved an immigration consultancy from 78291 to 78550 on both of its policies and credited $234.90. Earlier years weren’t refunded.
Sources: ACC — Sort out a problem with your levy invoice (last published 16 September 2025, checked 30 September 2026); ACC Levy Guidebook 2026/27 (checked 30 September 2026); ACC — Request an independent review (last published 4 November 2025, checked 30 September 2026); ACC credit notes on a CheckACC user’s account (shown with the owner’s permission, identifying details removed) (checked 29 September 2026)
Building supplies stores that sell to both the public and the trade used to sit between two codes: hardware and building supplies retailing (52330) and timber wholesaling (45310). In December 2023 the Court of Appeal held that a single integrated store can be doing both, and that the law then requires the higher-rated code. At 2026/27 rates that’s $1.45 per $100 against $0.69 for retailing.
MBIE’s regulatory impact statement of 25 November 2024 noted that applying the ruling across the industry would sharply raise levies for mainly-retail stores, and proposed a new unit. From 2025/26 there is one: 52329, “Home improvement goods trading – multiple product ranges”, for stores selling home improvement goods, building supplies and timber to both the public and the trade. Its rate is $0.99 for 2025/26, $0.97 for 2026/27 and $1.01 for 2027/28.
Stores selling a single product line, or to only one kind of customer, keep their existing code. The guidebook itself never says why 52329 appeared — that’s only in MBIE’s paper.
Sources: ACC v Anderson & O’Leary Ltd [2023] NZCA 654 (checked 29 September 2026); MBIE — Regulatory Impact Statement: New classification unit for home improvement stores (25 November 2024) (paragraphs 13, 15, 45, 46 and 52, checked 29 September 2026); Work Account Levies Regulations 2025 (SL 2025/17), schedules 1–3 (CU 52329, 52330 and 45310, checked 29 September 2026); ACC Levy Guidebooks 2022/23 to 2026/27, levy rate tables (cross-checked against the schedules of the Work Account Levies Regulations 2022 and 2025 — 8,055 figures, no differences, checked 25 September 2026)
Tell the check what your business does, and it tests the code on your invoice against the guidebook and the court decisions. Check your invoice — free