How is child maintenance calculated by the Child Maintenance Service?

Full answer

The Child Maintenance Service (CMS) uses a formula based primarily on the paying parent's gross income, rather than negotiation between parents, though parents can still agree a private arrangement outside the CMS formula if both prefer. **Gross income is the starting point** Unlike many tax and benefit calculations that use net or take-home income, CMS maintenance is based on the paying parent's GROSS weekly income (from HMRC records, typically the most recent tax year), less any pension contributions -- other deductions such as Income Tax and National Insurance are NOT subtracted before applying the maintenance percentage. **The percentage rates at the standard rate band** For gross weekly income between the basic threshold and an upper limit, the standard rate applies: broadly 12% of gross weekly income for one child, 16% for two children, and 19% for three or more children -- these percentages apply to income within the standard band, with a different, lower percentage rate applying to any income above that band up to the overall maximum considered. **Adjustments for shared care** If the child stays overnight with the paying parent for at least 52 nights a year (roughly one night a week on average), the calculated maintenance amount is reduced on a banded basis, with greater overnight care resulting in a larger reduction -- at very high levels of shared care (broadly equal), maintenance may reduce substantially or even become nil in some circumstances. **Adjustments for other children the paying parent supports** If the paying parent has other children living with them (from a different relationship), their gross income is first reduced by a percentage BEFORE the maintenance percentage for the child(ren) being assessed is applied, recognising their existing financial responsibilities. **Worked example** A paying parent has gross weekly income of £600 and one child being assessed, with no shared care nights and no other children living with them. At 12% of £600, this gives a basic weekly maintenance liability of £72. If the child instead stays with the paying parent for around one night a week on average (52+ nights a year), a shared care reduction would apply, lowering the weekly amount. **Very low or very high incomes** Below a minimum income threshold, a flat-rate or reduced-rate weekly amount applies instead of the percentage formula; above the maximum gross weekly income considered by the CMS formula, the receiving parent may need to apply to court for a 'top-up' order for maintenance above the CMS-calculated amount. **Practical tip** Use the official CMS calculator on gov.uk for a formal estimate, since it accounts for shared care nights, other children, and the exact banded percentage structure more precisely than a simple percentage-of-income estimate, and remember gross (not net) income is the basis for the whole calculation.

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