Child support in New Zealand, how it is calculated and how to challenge it

Last updated 20 June 2026. This is general information, not legal advice.

Child support is one of the most emotionally charged things separated parents deal with, and also one of the most misunderstood. People assume the amount is plucked from the air, or that whoever earns more simply pays a set percentage, when in fact it runs on a defined formula built around both parents’ incomes and how the care of the children is shared. Understanding how that formula works, and the ways it can be adjusted when it does not fit, is what lets you check whether your assessment is right and do something if it is not.

This guide explains how child support is arranged and calculated, how care changes it, what to do if your income changes, and how to challenge an assessment that does not reflect your situation. It is general information, not legal advice, and the figures quoted are for the 2026/2027 child support year and are updated annually.

Three ways to arrange child support

Child support in New Zealand is governed by the Child Support Act 1991 and administered by Inland Revenue. There are three ways parents can arrange it.

• A private arrangement. You and the other parent simply agree what is paid, between yourselves, without involving Inland Revenue. This works where parents are on good terms, but it has no official backing, so if payments stop you have no enforcement through the system.
• A voluntary agreement. You agree an amount and register it with Inland Revenue, which then collects and enforces it. This gives the certainty of the official system around an amount you both chose.
• A formula assessment. You apply to Inland Revenue, which calculates the amount using the formula and collects it. This is the default where parents cannot agree, and it is the route most people are on.

If a parent receives a sole parent benefit, they are generally required to be on a formula assessment through Inland Revenue rather than a private arrangement.

How the formula works

The formula assessment is not a flat percentage. It is an income-sharing model that tries to work out the cost of raising the children and split it between the parents in proportion to their incomes, after recognising the care each provides. In simplified terms, it works like this.

1. Each parent’s adjusted taxable income is worked out.
2. A living allowance, an amount set aside for that parent’s own living costs, is subtracted, along with any allowances for other dependent children, to give each parent’s child support income.
3. The two child support incomes are added together, and each parent’s share of that combined income is worked out as a percentage.
4. Each parent’s share of the care, based on the number of nights they have the children, is worked out as a care cost percentage.
5. Their income share is compared with their care share, and the parent whose income share is higher than their care share pays the difference, scaled by the estimated cost of the children for their ages.

The effect is that the parent who earns more, and provides less of the day-to-day care, pays child support to the other, and the size of it moves with both income and care. Inland Revenue has an online estimator that lets you put in the figures and see the result, which is the easiest way to sense-check your own assessment.

How care changes the amount

Care is one of the two big levers, and it is the one parents most often get wrong on their assessment. The formula only recognises a parent’s care once it reaches at least 28% of nights, which is about two nights a week, or 103 nights a year. Below that threshold, the time is not counted as shared care in the formula.

Once you are over that line, the care reduces what you pay or increases what you receive, and it steps up as the share of nights rises. A parent who has the children around a third of the time is recognised as carrying a real share of the costs, and the assessment reflects that. Because the number of nights drives the result, it is important that the nights recorded on your assessment actually match the real arrangement. If your care has changed, or was recorded wrongly, tell Inland Revenue, because an out-of-date care percentage is one of the most common reasons an assessment is too high or too low.

The minimum and the living allowance

Two figures shape the floor and the cushion in the formula.

The minimum annual rate means almost every liable parent pays something. For the 2026/2027 year the minimum is $1,211 a year, roughly $23 a week, and it applies even to a parent on a very low income or a benefit, unless they have a substantial share of the care.

The living allowance is the amount of a parent’s own income that is protected before child support is calculated, recognising that the paying parent has to live too. For 2026/2027 it is a single flat figure of $30,557 for most parents, or $34,252 for a parent on a supported living payment, and unlike the old rules it no longer changes according to whether the parent has a partner. If a parent is supporting other dependent children, that is recognised separately through a dependent child allowance, which further reduces their child support income. This is why a change in a paying parent’s family, such as a new child to support, can change the figure.

If your income drops

A standard assessment is based on your income from a previous tax year, which is a problem if your income has since fallen, because you can be assessed on money you are no longer earning. The fix is to estimate your income.

If you expect your income for the year to be at least 15% lower than the income your assessment is based on, you can elect to estimate it, and Inland Revenue will reassess your child support on the lower figure. This is important to do promptly if you lose a job or your hours are cut, because it stops arrears building up on an income you do not have. The trade-off is that an estimate is squared up against your actual income at the end of the year, so if you under-estimate you will owe the difference, and you should estimate honestly.

If the assessment is wrong, an administrative review

The formula is one size fits all, and sometimes it produces a result that does not fit real circumstances. The main way to change that is an administrative review.

An administrative review is decided not by Inland Revenue’s ordinary staff but by an independent review officer, and it can only be granted on one of 11 set grounds. Those grounds include things like the high cost of travelling to have contact with the children, the special needs of a child, costs of supporting the child that the formula does not capture, property or financial resources that a parent’s taxable income does not reflect, and a parent’s earning capacity being higher than their declared income suggests. You apply in writing setting out which ground applies and the evidence for it, the other parent gets to respond, and the reviewer can decide to change the assessment, up or down, or leave it as it is.

The review is the right tool where your situation is genuinely unusual in one of those recognised ways. It is not a way to re-argue the formula itself or simply complain that the amount feels too high, so the key to a successful review is showing your circumstances fit one of the grounds with real evidence.

Objections and the Family Court

There are two further routes beyond a review. You can lodge a formal objection to certain Inland Revenue decisions, such as a decision about whether you are even a liable parent or how a particular rule was applied, within the time limit Inland Revenue sets out. And the Family Court can make orders in some child support matters, including departure orders that change an assessment, and it hears appeals from administrative review decisions.

For most people, though, the administrative review is the practical first step, and going to court is a later resort if the review does not resolve it. Free guidance is available from a Community Law Centre, and Inland Revenue’s own material sets out the objection and review timeframes.

If you receive a benefit

One of the biggest recent changes affects sole parents on a benefit. From 1 July 2023, a sole parent receiving the benefit at the sole parent rate now receives the full amount of child support that Inland Revenue collects for their children, rather than the state keeping part of it to offset the benefit. This was a significant shift that put more money directly to those families.

The other side of that change is that child support received is now treated as income for working out benefit entitlement, so it can affect the amount of benefit paid. If you are on a benefit and receiving child support, it is worth understanding how the two interact, and Work and Income can explain how your child support affects your particular situation.

The takeaway

Child support is a formula, not a guess, and that is good news, because it means you can check it. The amount turns on both parents’ incomes, the living allowance, and above all the share of nights each parent has the children. If your care or income has changed, tell Inland Revenue and, if your income has dropped by 15% or more, estimate it. If the formula genuinely does not fit your circumstances, an administrative review on one of the 11 grounds is the way to adjust it. Keep your care arrangements and income details accurate and up to date, because that is what keeps the assessment fair.

Related guides

• Relationship property in New Zealand, who gets what in a separation
• Making a will in New Zealand and dying without one

Frequently asked questions

How is child support calculated in New Zealand

By a formula based on both parents’ incomes, the number of nights each has the children, and a living allowance set aside for each parent’s own costs. It is an income-sharing model, not a flat percentage. The parent whose income share is higher than their care share pays the difference, scaled by the estimated cost of the children. Inland Revenue has an online estimator you can use.

How much care do I need before it reduces my child support

At least 28% of nights, which is about two nights a week or 103 nights a year. Below that, the care is not counted as shared care in the formula. Once you are over the threshold, having the children more nights reduces what you pay or increases what you receive, so it is important the nights on your assessment match the real arrangement.

What is the minimum child support payment

For the 2026/2027 year the minimum annual rate is $1,211, about $23 a week. It applies to most liable parents even on a low income or a benefit, unless they have a substantial share of the care. The figure is updated each year.

Can I lower my child support if my income drops

Yes. If you expect your income for the year to be at least 15% lower than the income your assessment is based on, you can estimate your income and Inland Revenue will reassess you on the lower figure. Do it promptly to stop arrears building up. The estimate is squared up against your actual income at year end, so estimate honestly.

How do I challenge a child support assessment

Apply for an administrative review, decided by an independent reviewer on one of 11 grounds, such as the high cost of contact, a child’s special needs, or income that does not reflect a parent’s real means. You set out the ground and evidence, the other parent responds, and the reviewer can change the assessment. Objections and the Family Court are further steps if needed.

Do I get the child support if I am on a benefit

Yes. Since 1 July 2023, a sole parent on the benefit at the sole parent rate receives the full child support Inland Revenue collects for their children, rather than the state keeping part of it. The flip side is that child support received now counts as income for assessing your benefit, so it can affect how much benefit you are paid.

Can we just sort out child support between ourselves

Yes, if you are on good terms you can make a private arrangement without Inland Revenue, or register a voluntary agreement so Inland Revenue collects an amount you both chose. A private arrangement has no official enforcement if payments stop. A parent receiving a sole parent benefit is generally required to be on a formula assessment rather than a private deal.

Have you sorted out a child support assessment in New Zealand, or had one changed through a review? Tell us how it went in the comments below.