If you employ people in New Zealand, you need to understand KiwiSaver. Not just the basics of "deduct 3% and send it to IRD" – but the actual rules that determine whether you're doing it correctly.
KiwiSaver seems straightforward until you start looking at the details. ESCT rates that need annual reviews. Opt-out windows that are stricter than most employers realise. Contribution calculations that your payroll system might be getting wrong.
Here's what you need to know, explained in plain English.
ESCT: the tax on your employer contributions
When you contribute to your employee's KiwiSaver, you also need to pay Employer Superannuation Contribution Tax (ESCT) on that contribution.
ESCT is calculated on whole dollars only. If the employer KiwiSaver contribution is $47.25, you calculate ESCT on $47, not $47.25. This matters because some payroll systems get this wrong and calculate on the full amount including cents.
KiwiSaver under or overpayments can’t be claimed back as the money is going into investment funds. Getting it wrong means your employee could lose twice – once on the underpaid contribution, and again on all the future investment growth that money would have earned.
The ESCT rate depends on your employee's income. There are five rates: 10.5%, 17.5%, 30%, 33%, and 39%. You work out which rate applies based on the employee's total income (salary plus your gross employer contributions) for the previous tax year.
You need to review these rates every year on 1 April. An employee who was on the 17.5% rate last year might have moved into the 30% bracket this year if they got a pay rise or worked more hours. If you don't update the rate, you're either overtaxing or undertaxing them.
Most payroll systems don’t remind you to do this annual review, but Employment Hero has a report that helps identify when ESCT rates need to be adjusted.
KiwiSaver opt out rules: what are they?
Employees can only opt out of KiwiSaver at the very beginning of their working life. Employees who choose to opt into KiwiSaver (rather than being automatically enrolled by their employer) cannot opt out at all.
If an employee has never been enrolled in KiwiSaver they must remember to opt out every time they start new employment – previously opting out doesn’t carry over to a new job.
They have a specific window to opt out: between day 14 and day 56 of starting work. Not day 1, and not whenever they feel like it – but between days 14 to 56.
If they miss that window, they cannot opt out – ever. They're in KiwiSaver for life (though they can take a savings suspension if they need to stop contributions temporarily).
Late opt-outs after day 56 can only be approved by IRD in specific circumstances – usually when the employer didn't provide the required information pack, or events outside the employee's control prevented them opting out on time.
Recent KiwiSaver changes: 16 and 17-year-olds
From 1 July 2025, 16 and 17-year-olds became eligible for government contributions to their KiwiSaver (if they contribute enough to qualify).
From 1 April 2026, employers must make compulsory contributions for 16 and 17-year-old employees who are KiwiSaver members and making employee contributions. This applies to part-time jobs, casual work, after-school jobs – any employment.
The catch: 16 and 17-year-olds are not automatically enrolled. Auto-enrolment still only happens at age 18. So these younger employees need to actively choose to join KiwiSaver, but once they do and they're contributing, you're required to make employer contributions.
If you employ teenagers, this is a change worth knowing about. Make sure your payroll system is set up to handle contributions for this age group from 1 April 2026.
KiwiSaver contribution rates are increasing
The default employee and employer contribution rates are increasing from 3%.
From 1 April 2026: 3.5%
From 1 April 2028: 4%
If your employees are contributing at the default rate, this will automatically increase on these dates. Employees can apply for a temporary rate reduction back to 3% if they need to, but otherwise the new rates apply automatically.
Your payroll system needs to be updated to reflect these changes on the right dates. Don't assume it will happen automatically – check with your payroll provider.
What to review annually
Every 1 April, you should be checking:
ESCT rates for all employees (have any moved into different income brackets?)
Whether any employees have had work pattern changes that affect their KiwiSaver
That your payroll system settings still match current legislation
That contribution rates are correct (especially important in the years when default rates are changing)
This annual review catches issues before they become compliance problems. An employee being overtaxed on ESCT for a full year creates frustration when they realise. An employee being undertaxed creates a tax bill they weren't expecting.
Getting it right
KiwiSaver compliance isn't complicated, but it does require attention to detail and regular reviews. The rules are specific, the windows for opt-outs are strict, and the annual ESCT review is easy to forget.
If you're not confident your KiwiSaver payroll settings are correct, or if you've never done an annual ESCT review and you're not sure where to start, I’d love to help you. A payroll review will identify whether your settings are correct and whether any employees have been over or undertaxed.
About the author
Karyn Campbell is a New Zealand payroll consultant and founder of Payroll Consult. With 5+ years running her own consultancy and a background in payroll software – including roles across client support, onboarding, and partnership management at a leading NZ payroll provider – Karyn brings a rare combination of technical knowledge and real-world compliance experience. She works with business owners, bookkeepers, and payroll teams across New Zealand, specialising in payroll audits, system reviews, and fixing complex payroll issues for teams that don’t work a typical 9-5.
