Glossary · UK
What is Child Maintenance Service (CMS)?
The government statutory service that calculates, and can collect and enforce, child maintenance payments from a paying parent to a receiving parent, based on the paying parent's gross weekly income and the number of qualifying and relevant children.
Full Definition
The Child Maintenance Service (CMS) is the UK government's statutory service for arranging child maintenance where separated parents cannot agree a family-based arrangement between themselves, or where an existing arrangement has broken down. Either parent can apply, and the CMS calculates an amount the paying parent (the parent the child does not mainly live with) should pay the receiving parent, based primarily on the paying parent's gross weekly income from HMRC records, the number of "qualifying children" the calculation covers, and the number of other "relevant" children living with the paying parent, since maintenance for a first family is calculated with some allowance made for the cost of supporting children in a second household too. The standard calculation applies banded percentage rates to the paying parent's gross weekly income after deducting an allowance for other relevant children and pension contributions: broadly 12% for one qualifying child, 16% for two, and 19% for three or more, on income up to a set upper threshold, with a reduced percentage rate applying to any income above that threshold up to a further ceiling, beyond which the paying parent's income is no longer counted for CMS purposes and the receiving parent would need to apply to court separately for a "top-up" order if seeking more. The amount payable is also adjusted for shared care, with a step reduction applied where the child stays overnight with the paying parent for a set number of nights a year, and a minimum flat-rate or nil assessment applies to paying parents on very low income or certain benefits. Worked example: a paying parent has a gross weekly income of £600 and two qualifying children who live mainly with the other parent, with no other relevant children and no shared care nights above the basic threshold; applying the 16% rate for two children gives a basic calculation of £96 a week; if the children instead stayed overnight with the paying parent for around 52-103 nights a year, a one-seventh reduction would be applied to reflect that shared care, lowering the weekly liability to roughly £82 -- illustrating how both income and the actual pattern of overnight care directly change the CMS assessment, not just the number of children involved.