About the UK Child Maintenance Calculator
This UK child maintenance calculator follows the Child Maintenance Service (CMS) formula in Schedule 1 to the Child Support Act 1991 and the 2012 calculation regulations. Enter the paying parent’s yearly gross income, any pension contributions, the number of children the maintenance is for, other children living with the paying parent, and how many nights a year the children stay over with them. It shows which rate applies — nil, flat, reduced or basic — and the weekly, monthly and yearly amount.
It is useful for separated parents agreeing a family-based arrangement, paying parents checking a CMS letter, and receiving parents deciding whether to apply. The CMS rates and thresholds used here (the £7 flat rate, £100 and £200 reduced-rate bands, £800 and £3,000 income limits) are those in force for 2026.
The estimate assumes all the children have the same number of overnight stays and that the case is a single paying parent and a single receiving parent. It does not model variations for extra income or special expenses, income above £3,000 a week (which courts can top up), or the default rate used when income is unknown. Collect and Pay fees can be shown if the CMS collects the money for you.
With the default inputs, the weekly child maintenance is £122.74. Change any value above to recalculate instantly.
How to use the uk child maintenance calculator
- 1Enter the paying parent’s yearly gross income and any personal pension contributions.
- 2Enter how many children the maintenance is for and any other children living with the paying parent.
- 3Enter the number of nights a year the children stay with the paying parent.
- 4Tick the benefits box if the paying parent receives a qualifying benefit or State Pension.
- 5Read the weekly amount and switch on Collect and Pay to see the fees.
Formula and method
Gross weekly income I is the yearly gross income (after deductible pension contributions) divided by 365 and multiplied by 7, capped at £3,000. Below £7 the nil rate applies; from £7 to £100 (or if the paying parent receives a prescribed benefit) the flat rate is £7. Between £100 and £200 the reduced rate is £7 plus a percentage T of the income above £100, where T depends on the number of qualifying and other children. From £200 the basic rate applies: 12%, 16% or 19% of the first £800 for one, two or three-plus children, and 9%, 12% or 15% of the rest, after first reducing income by 11%, 14% or 16% for one, two or three-plus other children in the household.
Shared care then subtracts one-seventh for 52–103 nights a year, two-sevenths for 104–155, three-sevenths for 156–174 and one-half for 175 or more, with a further £7 a week per child at the one-half level. The amount cannot fall below £7 a week. For a paying parent on the benefit flat rate, 52 or more nights reduces the amount to nil.
- I
- Gross weekly income (yearly ÷ 365 × 7, max £3,000)
- I′
- Income after the reduction for other children in the household
- p₁, p₂
- Basic-rate percentages up to £800 and above £800
- T
- Reduced-rate percentage from regulation 43
Worked examples
£40,000 income, 2 children, no shared care
£40,000 ÷ 365 × 7 is £767.12 a week, under the £800 limit, so the basic rate is 16% for two children: £122.74 a week, or about £531.87 a month.
£65,000 income, 1 child, 1 other child at home, 104 nights
Weekly income of £1,246.58 is first cut by 11% for the other child, to £1,109.45. The basic rate is 12% of £800 (£96) plus 9% of £309.45 (£27.85) = £123.85. With 104 nights, two-sevenths comes off, leaving £88.46 a week.
Reduced rate: £8,000 income, 1 child
£8,000 a year is £153.42 a week, inside the £100–£200 reduced band. The amount is £7 plus 17% of the £53.42 above £100, which is £16.08 a week.
£30,000 income, 2 children, 182 nights (equal care)
The basic rate is 16% of £575.34 = £92.05. At 175+ nights it is halved to £46.03, then reduced by £7 for each of the two children, leaving £32.03 a week.
Frequently asked questions
How much child maintenance will I pay in the UK?+
For gross weekly income of £200 to £800, the CMS basic rate is 12% of gross income for one child, 16% for two and 19% for three or more. Income above £800 a week is charged at 9%, 12% or 15%. The total is then reduced for other children you support and for overnight stays.
How do overnight stays reduce child maintenance?+
From 52 nights a year the amount falls by one-seventh, from 104 nights by two-sevenths, from 156 nights by three-sevenths, and at 175 nights or more it is halved and cut by a further £7 a week per child. It cannot go below £7 a week.
Is child maintenance based on gross or net income?+
The CMS uses gross income — before tax and National Insurance — usually from the latest HMRC tax year. Personal pension contributions can be deducted, and the yearly figure is converted to a weekly one by dividing by 365 and multiplying by 7.
What is the flat rate of child maintenance?+
The flat rate is £7 a week. It applies if the paying parent earns £100 a week or less, or receives a prescribed benefit or pension such as State Pension or contribution-based JSA. Below £7 a week of income, or in some specific circumstances, the nil rate applies.
What are the CMS Collect and Pay fees?+
Using Direct Pay is free. With Collect and Pay, the paying parent pays a 20% fee on top of each payment and the receiving parent has 4% deducted from what they receive.
Is there a maximum amount of child maintenance?+
The CMS ignores gross income above £3,000 a week, so for one child the maximum basic rate is £294 a week before reductions. Where income is higher, the receiving parent can ask a court for an additional top-up order.
Results are general estimates and not legal advice. Laws vary by jurisdiction — consult a qualified attorney.
Sources
- Child Support Act 1991, Schedule 1 (legislation.gov.uk)
- Child Support Maintenance Calculation Regulations 2012, reg. 43 (reduced rate)
- Child Support Maintenance Calculation Regulations 2012, reg. 35 (historic income)
- GOV.UK — How child maintenance is worked out
- GOV.UK — Child Maintenance Service fees and charges