How the CMS works out child maintenance
The Child Maintenance Service (CMS) uses a fixed formula based on the paying parent's gross weekly income, which is income before tax, minus any pension contributions. It usually gets this figure straight from HMRC. The formula then looks at how many children the maintenance is for, any other children the paying parent supports at home, and how many nights the children stay over.
The rates
| Gross weekly income | Rate | What's paid |
|---|---|---|
| Under £7 | Nil | Nothing |
| £7 to £100, or on certain benefits | Flat | £7 a week |
| £100.01 to £199.99 | Reduced | £7 plus a percentage of income over £100 |
| £200 to £800 | Basic | 12% for 1 child, 16% for 2, 19% for 3 or more |
| £800.01 to £3,000 | Basic plus | Basic rate on the first £800, plus 9%, 12% or 15% on the rest |
For the reduced rate, the percentage of income over £100 is 17% for 1 child, 25% for 2 and 31% for 3 or more, a little lower if the paying parent also supports other children at home.
Other children at home
If the paying parent lives with other children they support (their own or a partner's, including those who get Child Benefit for them), their income is reduced before the percentages are applied: by 11% for 1 other child, 14% for 2 and 16% for 3 or more.
Shared care
If the children stay overnight with the paying parent, maintenance goes down:
| Nights a year | Reduction |
|---|---|
| 52 to 103 | One-seventh |
| 104 to 155 | Two-sevenths |
| 156 to 174 | Three-sevenths |
| 175 or more | Half, plus an extra £7 a week for each child |
Shared care can't usually bring the amount below £7 a week.
Worked examples
£30,000 a year, one child
£30,000 ÷ 52 = £576.92 a week. 12% of that is £69.23 a week, about £300 a month.
£50,000 a year, two children, 104 nights
£50,000 ÷ 52 = £961.54 a week. 16% of the first £800 is £128, and 12% of the remaining £161.54 is £19.38, giving £147.38. Two-sevenths off for shared care leaves £105.27 a week.
£150 a week, one child
Reduced rate: £7 plus 17% of £50 = £15.50 a week.
Family-based or CMS arrangement?
Parents can agree maintenance between themselves without the CMS, and many use the CMS formula as a starting point. If you can't agree, either parent can apply to the CMS. With Direct Pay, the CMS works out the amount and parents pay each other directly with no collection fees. With Collect and Pay, the CMS takes the money and passes it on, and fees are added for both parents.
- Child Benefit and child maintenance are separate: see the Child Benefit calculator.
- Child maintenance received doesn't reduce Universal Credit. Try the Universal Credit calculator.
- This calculator follows the scheme used in England, Wales and Scotland. Northern Ireland has its own Child Maintenance Service with the same formula.
Frequently asked questions
How is child maintenance calculated in the UK?
The CMS uses the paying parent's gross weekly income minus pension contributions. Between £200 and £800 a week they pay 12% for one child, 16% for two and 19% for three or more, with lower rates on income above £800 and reductions for other children and shared care.
How much child maintenance do I pay on £30,000 a year?
For one child it's about £69.23 a week, or £300 a month, if there are no other children at home and no shared care.
Does shared care reduce child maintenance?
Yes. 52 to 103 nights a year reduces it by one-seventh, rising to half plus £7 per child a week for 175 nights or more.
What is the minimum child maintenance payment?
The flat rate is £7 a week. It applies if gross weekly income is £100 or less, or the paying parent gets certain benefits.
Is there a maximum child maintenance?
The CMS ignores gross income over £3,000 a week. Above that, the receiving parent can ask a court for a top-up order.
Last reviewed October 2026 using 2026/27 figures. This is an estimate using the CMS formula. The CMS uses HMRC figures and may calculate a different amount.