Simon Chadwick
Founder, Orbit Money
Method: GOV.UK CMS formula (2012 scheme)Updated: 16 July 2026Sources: gov.uk (how it works), gov.uk (rates)
How the CMS works out child maintenance
The Child Maintenance Service, the body that replaced the old Child Support Agency (CSA), uses a set formula rather than a judgement about need. It starts with the paying parent’s gross weekly income, the figure before Income Tax and National Insurance but after pension contributions. That income places the case into one of five rates, then two reductions can apply: one for the nights the children stay with the paying parent, and one for other children living in their household.
The five CMS rates
| Rate | Gross weekly income | Amount |
|---|---|---|
| Nil rate | Under £7 gross a week (student, prisoner, some benefits) | £0 |
| Flat rate | £7 to £100 a week, or on certain benefits | £7 |
| Reduced rate | £100.01 to £199.99 a week | £7 + a percentage |
| Basic rate | £200 to £800 a week | 12% / 16% / 19% |
| Basic plus rate | £800.01 to £3,000 a week | 9% / 12% / 15% on the top slice |
Income above £3,000 a week is not counted by the CMS. The receiving parent can apply to the court for a top-up on income over that cap.
Basic and basic plus percentages
On the basic rate, maintenance is a percentage of gross weekly income up to £800. The slice of income between £800 and £3,000 is charged at the lower basic plus rate.
| Children | Up to £800/wk | £800–£3,000/wk |
|---|---|---|
| 1 child | 12% | 9% |
| 2 children | 16% | 12% |
| 3 or more children | 19% | 15% |
If the paying parent has other children living with them, their gross income is reduced first, by 11% for one child, 14% for two, or 16% for three or more, before the percentage above is applied.
Shared care and overnight stays
The more nights a year the children spend with the paying parent, the lower the payment. The reduction runs in bands.
| Nights per year | Reduction |
|---|---|
| 52 to 103 nights | 1/7 off |
| 104 to 155 nights | 2/7 off |
| 156 to 174 nights | 3/7 off |
| 175 nights or more | Half off, plus a further £7 per child |
How to use this calculator
- Enter the paying parent's gross income, weekly or annual, before tax but after pension.
- Choose how many children the maintenance is for.
- Add the number of nights a year the children stay overnight with the paying parent.
- Select any other children living in the paying parent's household.
- Read the estimated weekly and monthly maintenance, with the rate and reductions shown.
Frequently asked questions
How is child maintenance calculated in the UK?
The Child Maintenance Service works from the paying parent's gross weekly income, before tax and National Insurance but after pension contributions. It picks one of five rates. On the basic rate, that is 12% of gross weekly income for one child, 16% for two, and 19% for three or more, on income up to £800 a week. Income between £800 and £3,000 is charged at a lower basic plus rate of 9%, 12% or 15%. The figure is then reduced for nights the children spend with the paying parent and for other children living in their household. Income above £3,000 a week is not counted by the CMS.
Does child maintenance go down with overnight stays?
Yes. The more nights a year the children stay overnight with the paying parent, the lower the payment. From 52 to 103 nights the amount drops by one seventh, 104 to 155 nights by two sevenths, and 156 to 174 nights by three sevenths. At 175 nights or more the amount is halved, then reduced by a further £7 a week for each child. If shared care is roughly equal, the payment can fall to nothing.
What counts as income for child maintenance?
The CMS uses gross weekly income, which is earnings before Income Tax and National Insurance are taken off, but after any occupational or personal pension contributions. It normally comes from the paying parent's latest tax information held by HMRC. Only income up to £3,000 a week is counted. If the paying parent earns more than that, the receiving parent can apply to the court for a top-up order on the excess.
Do I have to pay child maintenance with 50/50 shared care?
Not always. Where care is shared equally, the CMS can reduce the payment to nil. That said, one parent may still pay if there is a clear gap in income between the two households, or if the day-to-day care is judged to sit mainly with one parent. Equal overnights are the trigger for the largest shared-care reduction, so the number of nights matters.
How much child maintenance should a father pay for one child?
On the CMS basic rate, one child is 12% of the paying parent's gross weekly income up to £800 a week, with 9% on income between £800 and £3,000. So a parent earning £500 a week gross with no other children and no shared care would pay about £60 a week. The figure falls once overnight stays or other children in the household are taken into account.
What is the difference between a CMS calculation and a private arrangement?
A private, or family-based, arrangement is one you agree directly with the other parent, for any amount you both accept, with no fees. A CMS calculation is the statutory figure the Child Maintenance Service works out using the formula, which it can collect and enforce if payments are missed. Many parents use this calculator to see the statutory figure first, then decide whether to arrange payments privately or through the CMS.
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About the author
Simon Chadwick
Founder of Orbit Money
Simon is the founder of Orbit Money, a tool that helps people track subscriptions and recurring spend. He builds Orbit's free money calculators and writes about personal finance for UK and Australian readers.
More from Simon →This tool gives an estimate of the statutory CMS calculation, not the binding figure on your case, and is a guide, not legal advice.