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Budget 2024: The Government has announced FamilyBoost, a proposed new childcare payment to help eligible families with the rising costs of Early Childhood Education (ECE). Find out more:

Use our calculator to work out the possible amount of monthly child support and who might be the liable parent or receiving carer.

What is a formula assessment?

A formula assessment is the most common form of child support agreement. Parents and non-parent carers can apply to us for a formula assessment.

Based on each parent or non-parent carer's circumstances we work out who pays child support and how much. We collect money from the paying parent and pass it on to the recipient.

Is a formula assessment a good option for me?

A formula assessment is a good option when you want us to decide the child support amount and make sure payments happen.

It is the best option if any of these are true:

  • you cannot agree on an amount
  • you want us to decide on an amount
  • you want us to make sure payments happen and follow up on missed payments
  • you do not get on with the other parent
  • you do not want to deal with the other person.

It is the only option if you are getting an Unsupported Child’s Benefit. You must apply for a formula assessment at the same time you apply for Unsupported Child's Benefit. The child support will go to the Goverment to help pay for your benefit - you will receive any remaining amount.

How does Inland Revenue decide on an amount?

We have a formula to work out a child support payment amount. The formula is based on all of these things:

  • both parents' incomes
  • both parents' living costs
  • the amount of time the child is in each parent's care
  • the cost of bringing up a child
  • the costs of other children in their care.

If the carer is not a parent then their income is not included in the formula.

How does it work?

A parent or non-parent carer applies to us for a child support assessment. After we have made our assessment each person gets a notice saying how much they will get or pay.

If the paying parent is employed or on a benefit, we will organise to have payments deducted from their income. Otherwise, the paying parent will usually set up automatic payments.

Payments are made monthly into the receiving carer's bank account as long as the paying parent makes their payment.

Tools to help 

2 minutes
Child support liability or entitlement calculator

This suggests an amount based on care arrangements and both parents' incomes.

Go to this tool

When does a formula assessment end?

A formula assessment ends when one of these happens:

  • a child no longer qualifies, usually when they turn 18
  • when both people agree to change to another type of agreement
  • when the person or people caring for the child choose to end the agreement.

Can I switch to another type of child support agreement?

If both people agree you can switch from a formula assessment to another kind of child support agreement.

If you are getting an Unsupported Child's Benefit for a child, you must stay on a formula assessment for that child.

You could switch to a voluntary agreement if both people can decide the amount. Inland Revenue will arrange the payments.

You could also choose a private agreement, which is where both people decide the amount and work out arrangements without us.

Voluntary agreement

Private agreement

What happens next

We cannot guarantee how much the child support will be, or who will be the liable parent or receiving carer. We won't know these details until you apply for a formula assessment and we've processed it.

Apply for a formula assessment

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Last updated: 30 Jun 2023
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