The ACC4618 form
The ACC4618 is the employer changes to business details form — the official way to tell ACC what your business actually does, which is what your levy classification hangs on. There is no fee and no deadline for this correction route.
Where to get it
Download it from ACC: the current ACC4618 (PDF). Self-employed? This form is not yours — update your details through MyACC for Business instead, or ring 0800 222 776 (Mon-Fri 8am-6pm).
What to write
Describe the activity as it is now, and date the change. Two things make an assessor's decision easy: naming the BIC code you believe is right (assessors work from BIC codes — "we believe the correct code is X" is a yes/no decision, "we do design now" makes them do the mapping), and not arguing figures. ACC calculates any adjustment from its own records.
Where to send it
Email the completed form to business@acc.co.nz. Keep a copy and note the date. ACC issues a credit or debit note if the reassessment changes anything; keep paying the current invoice while it is processed — a disputed classification does not pause a due date.
The step everyone misses
Update the BIC code with IRD as well (myIR secure mail, or 0800 377 774). ACC and IRD match data; fix only one side and the classification quietly reverts next year.
The checker fills this form's substance for you — activity wording, dates, target code — after walking you through whether the claim would survive at all.
Run the check firstSources: ACC4618 (PDF); ACC — sort a levy problem.