UK What this calculator does
The Child Maintenance Service does not weigh up what feels fair. It applies a published formula to the paying parent's gross weekly income, adjusts for how many nights the children stay overnight, and adjusts again for other children living in that household. This tool implements that formula so you can see the arithmetic rather than just a number.
It is genuinely useful to know your figure before you speak to anyone. Two parents who both understand how the calculation works tend to argue about it far less, and a solicitor's time is better spent on the things that are actually in dispute.
The five rate bands
Everything starts with gross weekly income — before tax and National Insurance, but after pension contributions.
| Nil rate | Under £7 a week, or the paying parent is a student, a prisoner, or aged 16–19 in full-time non-advanced education. Nothing is payable. |
|---|---|
| Flat rate | £7 a week, where gross weekly income is £7–£100, or certain benefits are received. |
| Reduced rate | £100.01–£199.99. £7 plus a percentage of the income above £100: 17% for one child, 25% for two, 31% for three or more. |
| Basic rate | £200–£800. 12% for one child, 16% for two, 19% for three or more. |
| Basic rate plus | £800.01–£3,000. The basic rate on the first £800, then 9% / 12% / 15% on the remainder. Income above £3,000 a week falls outside the formula. |
Two worked examples
One child, £35,000 a year, no overnight stays
£35,000 a year is about £673 gross a week, which falls in the basic rate band. One child attracts 12%, giving roughly £80.77 a week, or about £350 a month. With no overnight stays there is no shared-care reduction.
Two children, £52,000 a year, alternate weekends and half the holidays
£52,000 a year is £1,000 gross a week, which crosses into basic rate plus. Two children attract 16% on the first £800 (£128) plus 12% on the remaining £200 (£24), giving £152 a week before shared care. Alternate weekends plus half the school holidays lands around 104 nights a year, which cuts the figure by two sevenths — roughly £108.57 a week.
That second example shows why the overnight count matters so much. Moving from 103 to 104 nights changes the reduction band and, in this case, saves around £22 a week.
The shared-care bands, and an honest word about them
| 52–103 nights | Reduced by one seventh |
|---|---|
| 104–155 nights | Reduced by two sevenths |
| 156–174 nights | Reduced by three sevenths |
| 175+ nights | Halved, then a further £7 per child deducted |
Because the bands are wide and the cliff edges are sharp, a single extra night a fortnight can move you into a cheaper band while a dozen extra nights elsewhere change nothing at all. This creates a real and uncomfortable incentive to negotiate nights for financial rather than parenting reasons.
Our advice, for what it is worth: decide what genuinely suits the children, then calculate. Working backwards from the money is how people end up with arrangements that suit neither parent nor child.
Common questions
Does this apply in Scotland and Northern Ireland?
The formula applies across England, Wales and Scotland. Northern Ireland runs its own Child Maintenance Service using broadly the same rules but administered separately — see our child maintenance guide for the detail.
Is child maintenance affected by who the child lives with legally?
No. Maintenance follows the overnight count and income, not a court order about residence. Equally, paying maintenance does not purchase contact, and being refused contact does not excuse non-payment. The two are legally independent.
What if the paying parent is self-employed or hiding income?
The CMS uses HMRC data, which for a self-employed parent means declared taxable profit. Where you believe income is being understated, you can apply for a variation — for example on the grounds of unearned income, assets, or diversion of income. This is one of the situations where a solicitor genuinely earns their fee.
Does maintenance stop automatically at 16?
It usually continues while the child is under 20 and in approved full-time non-advanced education, such as A-levels. It does not automatically continue through university.
Should this go in a court order?
Child maintenance is generally handled by the CMS rather than the courts, but it usually sits alongside a wider financial settlement. That settlement should be made binding — see consent orders and clean breaks for why an informal agreement leaves claims open indefinitely.
Where to go next
If you need a binding assessment, apply through the Child Maintenance Service. For free impartial guidance on arrangements, GOV.UK Child Maintenance Options covers family-based arrangements, and Citizens Advice can help you work out what to do.
If the money is one part of a bigger separation, our guides cover pensions, the family home and what a divorce costs — or search the directory of family law solicitors for a firm near you.