UKHow is child maintenance calculated in the UK?
Child maintenance in the UK is calculated by the Child Maintenance Service (CMS) using a formula based on the paying parent’s gross weekly income, number of children, and how many nights per week the child stays with them.
What the Law Says
The legal framework for child maintenance calculation is set out in the Child Maintenance and Other Payments Act 2008, which established the Child Maintenance Service (CMS) and its statutory duty to assess and collect maintenance.
The CMS uses a standardised income-based formula to calculate how much the non-resident (paying) parent must pay each week. The amount depends primarily on their gross weekly income before tax and National Insurance, the number of children involved, and how many nights per week the child spends with them (‘shared care’).
There are five fixed percentage rates applied to gross weekly income: 12% for one child, 16% for two children, and 19% for three or more children — unless shared care applies (i.e., the child stays with the paying parent for at least 52 nights a year), in which case reductions apply. A minimum payment of £7 per week applies if the paying parent’s gross weekly income is below £100 or they receive certain benefits.
The calculation is reviewed annually and adjusted automatically where income changes are reported or detected via HMRC data sharing.
Statutory TextThe Secretary of State must make arrangements for the assessment and collection of child maintenance payments in accordance with this Part.
— Child Maintenance and Other Payments Act 2008, s. 1 — Duty to make arrangements
What to Do
Check if you’re eligible to use the CMS (e.g., both parents live in the UK, child is under 20 and in full-time education up to A-level equivalent)
Apply online via GOV.UK or call the CMS to request a calculation
Provide proof of income (e.g., payslips, P60, or self-assessment returns) and details of shared care arrangements
Review your calculated amount — you can ask for a mandatory reconsideration within one month if you disagree
Set up direct debit or arrange another payment method; late payments may incur enforcement action
Sources
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South KoreaNot legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.