Child maintenance is money paid by the parent who does not live with a child towards that child's everyday living costs. In the UK, parents can agree an amount between themselves, or they can ask the Child Maintenance Service, known as the CMS, to work it out and arrange it. The CMS usually follows six steps to work out the weekly amount, starting with the paying parent's gross weekly income taken from HM Revenue and Customs, and on the basic rate it takes 12% of that income for one child, 16% for two children and 19% for three or more. Payments normally continue until the child is 16, or 20 if they stay in full-time education up to A-level standard.

The parent who does not have main day-to-day care of the child is called the paying parent. The parent who has main day-to-day care is called the receiving parent. Child maintenance is separate from any court order about property or spousal maintenance, and it does not affect benefits: GOV.UK guidance notes that maintenance payments will not affect benefits the parents or children receive, including Universal Credit.

What is child maintenance?

Child maintenance covers how a child's living costs will be shared when parents live apart. It is a legal obligation, governed mainly by the Child Support Act 1991, and it applies whether or not the parents were married. The amount is worked out from income, not from what either parent thinks is fair, which is why the CMS formula matters so much to separated families.

Parents must have a child maintenance arrangement if their child is under 16, or under 20 if the child is still in full-time education. The arrangement can be informal, but an informal agreement has no enforcement behind it. That is the main reason parents turn to the CMS: it can calculate the amount, collect the payments and take action if a parent does not pay.

The two ways to arrange child maintenance

There are two routes, and parents can choose either one. The first is a family-based arrangement, where the parents agree between themselves how much will be paid and how often. This can be flexible, it costs nothing, and it can include things the CMS formula does not cover, such as school trips or clothes. But if the paying parent stops paying, the receiving parent has no official way to enforce the agreement.

The second route is through the Child Maintenance Service. The CMS works out the amount using its formula, and parents can then choose Direct Pay, where the paying parent pays the receiving parent directly, or Collect and Pay, where the CMS collects the money and passes it on. Direct Pay has no collection fees. Collect and Pay does: the paying parent pays 20% on top of the maintenance amount, and the receiving parent has 4% taken off what they receive.

Applying to the CMS costs a £20 application fee. You do not need to pay it if you are under 19, live in Northern Ireland, or are a victim of domestic abuse. You cannot use the CMS if you already have a court consent order less than a year old covering child maintenance.

How the CMS works out the amount

GOV.UK sets out six steps the CMS usually follows. First, it finds the paying parent's yearly gross income from information supplied by HMRC, using the latest tax year available. It also checks whether the paying parent is getting benefits. Student grants and loans do not count as income.

Second, it looks at things that could change the gross income figure, such as pension payments or other children the paying parent supports. Either parent can also ask for extra income, assets or expenses to be taken into account, which is called applying for a variation. Third, it applies one of five rates based on the paying parent's gross weekly income. Fourth, it takes into account the number of children the paying parent has to pay maintenance for, including other children living with them. Fifth, it decides the weekly amount. Sixth, it applies any reduction for shared care, where the child stays overnight with the paying parent.

The CMS rechecks the paying parent's income at an annual review each year, and it can recalculate sooner if there is a change of circumstances, such as a significant change in income, or if either parent applies for a variation.

The five CMS rates

One of five rates applies, depending on the paying parent's gross weekly income. The bands, as published on GOV.UK, are:

• Default rate: income unknown or not provided, £38 a week for one child, £51 for two children, £64 for three or more children
• Nil rate: gross weekly income below £7, nothing to pay
• Flat rate: gross weekly income of £7 to £100, or if the paying parent gets certain benefits, £7 a week
• Reduced rate: gross weekly income of £100.01 to £199.99, worked out using a formula
• Basic rate: gross weekly income of £200 to £3,000, worked out using a formula

If the paying parent's gross weekly income is more than £3,000, the CMS ignores the income above that figure, and the receiving parent can apply to the courts for extra child maintenance, known as a top-up order.

The percentages: 12%, 16% and 19%

On the basic rate, the CMS takes a percentage of the paying parent's gross weekly income, and the percentage depends on how many children the calculation covers. The percentages come from Schedule 1 to the Child Support Act 1991, and they are:

• One qualifying child: 12% of gross weekly income
• Two qualifying children: 16% of gross weekly income
• Three or more qualifying children: 19% of gross weekly income

If gross weekly income is above £800, a lower percentage applies to the part above £800: 9% for one child, 12% for two children and 15% for three or more. So a paying parent with one child and gross weekly income of £1,000 would pay 12% of the first £800, which is £96, plus 9% of the remaining £200, which is £18, giving £114 a week before any shared care reduction.

Before the percentages are applied, the income figure is reduced for other children living with the paying parent: by 11% for one other child, 14% for two, and 16% for three or more. On the reduced rate, for income between £100.01 and £199.99 a week, the CMS starts from the £7 flat rate and adds a percentage of the income above £100.

Shared care: how overnight stays change the amount

Shared care is when the paying parent's child stays overnight with them. The CMS can reduce the weekly amount if the parents agree the child will stay overnight for 52 nights a year or more, and the reduction depends on how many nights are agreed. The number of nights is based on a court order or an agreement between the parents.

For the reduced and basic rates, the reductions published on GOV.UK are:

• 52 to 103 nights a year: reduction of 14.29%, or one seventh
• 104 to 155 nights a year: reduction of 28.57%, or two sevenths
• 156 to 174 nights a year: reduction of 42.86%, or three sevenths
• 175 nights or more a year: reduction of 50%, plus an extra £7 a week

The payment cannot go below £7 a week. If the parents agree to at least 52 nights a year but cannot agree on the exact number above that, the CMS assumes shared care is only happening for 52 nights a year. For the flat rate, the rules are different: if the paying parent gets benefits and it is agreed the child stays overnight for 52 nights or more a year, they do not pay maintenance for that child, or for any other children living in the same household as that child. If the paying parent does not get benefits, overnight stays do not affect the flat rate amount.

When does child maintenance stop?

Child maintenance normally stops when the child reaches 16, unless they stay in full-time approved education or training. If they do, it can continue until they turn 20. The education must be full-time, meaning more than an average of 12 hours a week of supervised study or course-related work experience, and it must be non-advanced, up to and including A-level or equivalent.

If the child leaves education or training, maintenance stops on 31 August on or after their 16th birthday. If they leave later, it stops on the last day of February, May, August or November, whichever comes first. It also stops if the child starts an advanced course, such as a university degree, or a course paid for by an employer. Child maintenance is linked to Child Benefit, so parents need to tell HMRC about changes to the child's education or training, not the CMS. The paying parent may still need to make payments after regular maintenance stops, for example because they missed payments in the past.

What if circumstances change?

The amount can change when the case is reviewed each year, when either parent applies for a variation, or when the paying parent has a change of circumstances that affects income or expenses. Either parent can ask for other income and assets to be taken into account, including rental income over £2,500 a year, interest and dividends from savings and investments over £2,500 a year, gross earnings or a pension of at least £100 a week where the paying parent is on the flat rate, income the paying parent may be diverting, and assets such as shares, stocks, gold or money worth more than £31,250.

The paying parent can ask for expenses to be taken into account, including costs of keeping in regular contact with the child, costs of supporting a child with a disability or long-term illness who lives with them, repaying debts from a previous relationship, boarding school fees, and mortgage, loan or insurance payments for the home the parents used to share if the receiving parent and child still live there. Each type of expense must be more than £10 a week, except the costs of supporting a child with a disability or long-term illness, which can be less. After a variation is applied for, it can take up to three months for the payment amount to change.

Frequently asked questions

Can parents agree child maintenance privately? Yes. A family-based arrangement is free and flexible, but the CMS cannot enforce it if payments stop.

Does child maintenance affect benefits? No. GOV.UK guidance states that maintenance payments will not affect benefits, including Universal Credit.

What if the paying parent does not pay? The CMS can collect payments through Collect and Pay and take enforcement action, including deductions from earnings.

How much is the CMS application fee? £20, unless you are under 19, live in Northern Ireland, or are a victim of domestic abuse.

Do I need a calculator? GOV.UK has an official child maintenance calculator that shows what the government is likely to work out for you, but only a formal CMS calculation is binding.

Rules can differ in Northern Ireland, so check the official guidance for your part of the UK before acting.