Child Maintenance Calculator UK
Gross means before tax and National Insurance, after pension contributions. The CMS takes this figure from HMRC, not from a payslip. Only the first £3,000 a week counts.
Model: the CMS 2012 gross-income scheme, in the order the CMS applies it — reduce gross income for other children (11% / 14% / 16%), pick the rate band, apply the percentage for the number of children, then apply the shared-care reduction for overnight stays. Payments cannot fall below £7 a week on the basic or reduced rate. This is an estimate; the CMS calculation is final.
How the CMS formula works, step by step
The Child Maintenance Service does not weigh up what a child costs, what either parent can afford, or what either household needs. It runs a fixed formula, in a fixed order, every time. Step one: take the paying parent’s gross weekly income from HMRC — earnings before income tax and National Insurance, but after pension contributions. Step two: reduce it for any other children living with the paying parent: 11% off for one other child, 14% for two, 16% for three or more. Step three: work out which rate band the adjusted income falls into. Step four: apply the percentage for the number of children the maintenance is for. Step five: reduce it for shared care, based on how many nights a year the children stay with the paying parent.
The five rate bands are the heart of the formula. Below £7 a week gross, the nil rate applies and nothing is payable. From £7 to £100 a week, the flat rate is £7 a week, however many children there are. From £100.01 to £199.99, the reduced rate is £7 plus a percentage of the income above £100 — 17% for one child, 25% for two, 31% for three or more. From £200 to £800, the basic rate is 12% of gross weekly income for one child, 16% for two, and 19% for three or more. Above £800, the basic-plus rate applies the basic percentage to the first £800 and a lower percentage — 9%, 12% or 15% — to the income above £800. Only the first £3,000 a week of income counts; above that, the receiving parent can ask a court for a top-up.
The rate bands at a glance
| Gross weekly income | Rate | 1 child | 2 children | 3+ children |
|---|---|---|---|---|
| Under £7 | Nil | £0 | £0 | £0 |
| £7 – £100 | Flat | £7/week | £7/week | £7/week |
| £100.01 – £199.99 | Reduced | £7 + 17% over £100 | £7 + 25% over £100 | £7 + 31% over £100 |
| £200 – £800 | Basic | 12% | 16% | 19% |
| £800.01 – £3,000 | Basic plus | 12% to £800, then 9% | 16% to £800, then 12% | 19% to £800, then 15% |
How overnight stays change the amount
Shared care reduces the payment, but only if the child stays overnight with the paying parent for at least 52 nights a year. Daytime visits on their own do not count. The reduction is one-seventh for 52 to 103 nights a year, two-sevenths for 104 to 155 nights, three-sevenths for 156 to 174 nights, and a half for 175 nights or more, plus an extra £7 a week off for each child in that top band. The reduction applies per child, and the payment cannot fall below £7 a week on the basic or reduced rate. On the flat rate, 52 or more nights a year means nothing is payable at all.
| Nights a year | Reduction | £72/week becomes |
|---|---|---|
| 0 – 51 | None | £72.00 |
| 52 – 103 | One-seventh | £61.71 |
| 104 – 155 | Two-sevenths | £51.43 |
| 156 – 174 | Three-sevenths | £41.14 |
| 175 or more | Half, less £7 | £29.00 |
Worked examples
- £600 a week, 1 child, no overnight stays: basic rate, 12% × £600 = £72 a week (£312 a month, £3,744 a year).
- £600 a week, 1 child, 104 nights: £72 × (1 − 2/7) = £51.43 a week.
- £600 a week, 1 child, 175 nights: £72 ÷ 2 − £7 = £29 a week.
- £150 a week, 1 child: reduced rate, £7 + 17% × (£150 − £100) = £15.50 a week.
- £1,000 a week, 2 children: basic plus, 16% × £800 + 12% × £200 = £128 + £24 = £152 a week.
- £600 a week, 2 children, 1 other child at home: income reduced by 11% to £534; 16% × £534 = £85.44 a week.
- £50 a week, 1 child: flat rate, £7 a week. £5 a week: nil rate, £0.
Family-based arrangements, Direct Pay and Collect and Pay
Parents do not have to use the CMS. A family-based arrangement — an agreement between the parents, with or without the CMS calculator’s help — can be any amount both parents accept, and it can include non-cash help such as school uniforms or activities. If parents use the CMS, there are two ways to pay. Direct Pay means the paying parent pays the receiving parent directly, and there are no fees. Collect and Pay means the CMS collects the money and passes it on, and charges fees: 20% on top for the paying parent, and 4% taken from the receiving parent’s payment. The £20 application fee for using the CMS was removed on 26 February 2024. The government has said it intends to remove Direct Pay and move all cases to a single collection service, but that needs new law and was not in force when this page was checked.
When does maintenance stop, and what if it is not paid?
Child maintenance normally stops when the child turns 16, or at 20 if the child is still in approved education or training. It does not stop automatically on a birthday — the CMS or the parents’ arrangement needs to reflect the change, so tell the CMS when the circumstances change rather than assuming the payments will end by themselves. If the paying parent’s income changes, either parent can ask for a recalculation, and the CMS will use the new HMRC figure. A change of 25% or more in income is the threshold for recalculating on current income rather than the last complete tax year’s figure.
If maintenance is not paid, the consequences depend on how it is paid. Under Direct Pay, the receiving parent should contact the CMS, which can move the case to Collect and Pay and add the 20% collection fee for the paying parent. Under Collect and Pay, the CMS can take money directly from the paying parent’s earnings or bank account, and in serious cases it can ask a court to take away a driving licence or passport, or to send the paying parent to prison. Those are last resorts, but they exist because maintenance is a legal obligation, not a voluntary payment. If you are the paying parent and your circumstances change — you lose your job, or your income falls sharply — tell the CMS straight away rather than stopping payments, because arrears build up from the date the change should have been reported, not from the date you report it.
Related: Take Home Pay Calculator · Income Tax Calculator 2026/27 · Credit Card Payoff Calculator
Sources: GOV.UK, “How child maintenance is worked out” and “Telling the Child Maintenance Service about living arrangements” (2012 gross-income scheme: nil, flat, reduced, basic and basic-plus rates; other-children reductions 11%/14%/16%; shared-care reductions; £3,000/week cap); Child Support Maintenance Calculation Regulations 2012. Checked 13 November 2026.