How Is Child Maintenance Calculated in the UK?
Published 15 November 2026 · Family Finance
Try it nowChild Maintenance Calculator →The Child Maintenance Service (CMS) uses a set formula. Get a quick estimate with the child maintenance calculator.
Step 1: Gross weekly income
The CMS takes the paying parent’s income before tax and NI, minus pension contributions, usually from HMRC records. Annual income is divided by 52.
Step 2: Apply the rate
| Gross weekly income | Rate |
|---|---|
| Under £7 | Nil |
| £7–£100 | Flat £7 |
| £100–£200 | Reduced rate |
| £200–£3,000 | Basic rate: 12% / 16% / 19% for 1 / 2 / 3+ children on the first £800, then 9% / 12% / 15% |
Step 3: Other children
If other children live with the paying parent, income is reduced by 11%, 14% or 16% before the rate is applied.
Step 4: Shared care
Overnight stays with the paying parent reduce payments: 52–103 nights a year by one-seventh, up to half for 175+ nights.
Example
Gross income £36,400 (£700 a week), one child, no shared care: 12% × £700 = £84 a week, about £364 a month.
Family-based arrangements
Parents can agree an amount privately. Using the CMS calculation as a starting point often helps.
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15 Nov 2026