The Child Maintenance Service (CMS) does not weigh up what a child costs or what feels fair. It runs a fixed statutory formula off one main number: the paying parent's gross weekly income. On the most common rate, that parent pays 12% of gross weekly income for one child, 16% for two, and 19% for three or more, on income up to £800 a week, before reductions for shared care and other children. The rest is arithmetic.
Because the formula is fixed, you can work your own figure out in minutes. The fastest route is the official gov.uk child maintenance calculator, which applies the current rates for you: enter gross income, the number of children and the number of nights they stay over, and it returns a weekly amount. This guide explains what the calculator is doing under the bonnet, with worked examples, so you can sense-check its answer and understand how each factor moves the number. For live figures and long-run trends across the CMS caseload, see our UK child maintenance tracker.
The five CMS rates
Every calculation starts by placing the paying parent on one of five rates, set by their gross weekly income (gov.uk sets out how child maintenance is worked out):
- Nil rate: gross weekly income below £7, or the paying parent is a student, a prisoner, or aged 16 to 19 in full-time non-advanced education. No maintenance is due.
- Flat rate: £7 a week, where gross weekly income is between £7 and £100, or the paying parent receives certain benefits.
- Reduced rate: where gross weekly income is between £100.01 and £199.99. Maintenance is worked out on a sliding formula that sits between the flat rate and the basic rate, so it climbs gradually across that band.
- Basic rate: where gross weekly income is between £200 and £800. This is where most working parents sit.
- Basic plus rate: where gross weekly income runs above £800, up to the £3,000 ceiling. A second, lower percentage is added on the slice above £800.
The nil, flat and reduced rates cover parents on low or benefit incomes. The rest of this guide focuses on the basic and basic plus rates, which is where the percentages people ask about actually live.
What counts as gross weekly income
Gross weekly income is taxable income before tax and National Insurance but after any pension contributions. Crucially, the CMS does not usually ask what you earn today. It takes the figure HMRC holds for the latest available tax year: PAYE data for employees, and the most recent Self Assessment return for the self-employed. That historic figure stands unless current income differs from it by 25% or more, in which case the CMS can use the current figure instead.
Two consequences follow. First, a recent pay rise or drop may not show up straight away. Second, income above £3,000 a week gross (£156,000 a year) is ignored for the formula: that is the statutory ceiling, covered below.
The basic and basic plus percentages
On the basic rate, the paying parent pays a flat percentage of gross weekly income, set by the number of children in the case:
- One child: 12%
- Two children: 16%
- Three or more children: 19%
Those percentages apply to gross weekly income from £200 up to £800. Where income runs above £800, the basic plus rate adds a second, lower percentage on the slice between £800.01 and £3,000:
- One child: 9%
- Two children: 12%
- Three or more children: 15%
The two are stacked, not swapped. A higher earner pays the basic percentage on the first £800 and the lower basic plus percentage on everything from £800.01 to £3,000. This structure is set out in the Child Support Maintenance Calculation Regulations 2012.
Here are the two bands, and the Collect and Pay charges covered later, in one place:
| Rate element | One child | Two children | Three or more |
|---|---|---|---|
| Basic rate (gross weekly income £200 to £800) | 12% | 16% | 19% |
| Basic plus rate (slice from £800.01 to £3,000) | 9% | 12% | 15% |
| Collect and Pay: paying parent | Pays an extra 20% on top of the calculated amount | ||
| Collect and Pay: receiving parent | Receives 4% less than the calculated amount | ||
Reduction for other children in the household
Before the rates are applied, the CMS reduces the paying parent's gross weekly income to reflect other children they, or their partner, receive Child Benefit for (children who are not part of this case). The income is cut by:
- 11% for one other child
- 14% for two other children
- 16% for three or more other children
Only the reduced income is then run through the 12%, 16% or 19% rates. This is why a parent supporting children in more than one household pays less for each child than the headline percentage suggests.
Reduction for shared care (overnight stays)
The number of nights a year the child stays overnight with the paying parent reduces the maintenance in bands. The reduction is worked out per child:
- 52 to 103 nights: reduce by one seventh (about 14.29%)
- 104 to 155 nights: reduce by two sevenths (about 28.57%)
- 156 to 174 nights: reduce by three sevenths (about 42.86%)
- 175 nights or more: reduce by half, and take a further £7 a week off for that child
Where care is genuinely equal and neither parent provides the main day-to-day care, no maintenance may be payable at all. Overnight arrangements are agreed between the parents; the CMS applies whichever band the pattern falls into.
Three worked examples
Example 1: basic rate, one child, no shared care
A paying parent has gross weekly income of £500, one child in the case, no other children at home, and no overnight stays. The basic rate for one child is 12%.
- £500 × 12% = £60 a week.
That is the whole calculation: with no shared care and no other children to deduct for, nothing reduces it.
Example 2: basic plus rate, two children, with overnight stays
A paying parent has gross weekly income of £1,200, two children in the case, no other children at home, and the children stay 120 nights a year (the 104 to 155 band, a two-sevenths reduction).
- Basic rate on the first £800: £800 × 16% = £128.
- Basic plus on the slice from £800.01 to £1,200 (£400): £400 × 12% = £48.
- Subtotal before shared care: £128 + £48 = £176 a week.
- Shared care reduction of two sevenths (28.57%): £176 × (1 − 0.2857) = about £126 a week.
Example 3: basic rate with other children at home
A paying parent has gross weekly income of £700, one child in the case, and two other children living with them for whom Child Benefit is received. There is no shared care for the child in the case.
- Reduce income for two other children (14%): £700 × (1 − 0.14) = £602.
- Basic rate for one child (12%): £602 × 12% = about £72 a week.
These examples use the statutory percentages, but real cases can involve variations (for example where a parent has additional unearned income or assets). Always confirm your own figure with the gov.uk calculator, which is the authoritative tool.
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Direct Pay versus Collect and Pay
The CMS works out the amount, but how the money moves is a separate choice with a real cost attached:
- Direct Pay: the CMS calculates the figure and the parents arrange payment between themselves, usually by standing order. It is free.
- Collect and Pay: the CMS collects from the paying parent and passes the money on. The paying parent pays an extra 20% on top of the maintenance, and the receiving parent loses 4% of what they receive.
On the Example 1 figure of £60 a week, Collect and Pay would mean the paying parent hands over £72 and the receiving parent nets about £57.60. Over a year that gap is real money, which is why most families are steered towards Direct Pay unless payments have proved unreliable.
The £3,000 ceiling and court top-up orders
The statutory formula stops at £3,000 a week gross. Where the paying parent earns more, the CMS calculates up to that ceiling and no further. The receiving parent can then apply separately to the family court for a top-up order to reflect income above the line, under Schedule 1 of the Children Act 1989. Courts use the CMS figure as a starting point and adjust for the child's needs and the family's standard of living.
Schedule 1 also covers other situations the CMS cannot reach, such as lump sums, housing provision, or maintenance where a parent lives abroad. Those overlap with the wider financial settlement and are best considered alongside it; see our guide to divorce financial settlements and the financial settlements hub. Child maintenance for the day-to-day, though, remains a CMS matter for the vast majority of families.
How to use the gov.uk calculator
The official gov.uk child maintenance calculator is free and takes a couple of minutes. To get an accurate figure, have these to hand:
- The paying parent's gross annual income from the latest tax year (the calculator converts it to a weekly figure).
- The number of children the maintenance is for.
- The number of nights a year those children stay overnight with the paying parent.
- The number of other children living in the paying parent's household.
The result is a weekly amount using current rates. It is an estimate for planning: a formal CMS calculation can differ where income data or care arrangements are disputed. For a wider view of how CMS awards have moved across the caseload, our child maintenance tracker tracks the published data.
Where child maintenance sits in the bigger picture
Child maintenance is only one strand of separating a family's finances. It is decided by the CMS formula and stands apart from spousal maintenance, which is income between former partners and is agreed or ordered by a court on completely different principles. A family may have both running at once. If you are working through arrangements as separated parents, our page for separated parents pulls the relevant guides and tools together in one place.
Speak to a specialist
None of this is legal advice. The CMS formula covers most families cleanly, but the edges (income above the £3,000 ceiling, disputed self-employed earnings, top-up claims, or maintenance wrapped into a wider settlement) are where a family law professional earns their keep. We work with family law firms across England and Wales who field these questions every day. Set out your circumstances through our contact page and we will arrange a first conversation with no obligation. We are not a law firm and cannot advise you directly; a firm we put you in touch with may pay us a fee, which never changes what you pay.