Child Maintenance Explained: How the CMS Calculates What You Pay or Receive

Both parents are responsible for supporting their children financially, regardless of contact arrangements, marital status, or which parent has main day-to-day care - and the Child Maintenance Service (CMS) uses a specific, calculable formula that’s worth understanding whether you’re paying or receiving. The CMS covers England, Wales and Scotland (Northern Ireland has its own Child Maintenance Service), and maintenance is payable for children under 16, or under 20 if they’re in approved full-time non-advanced education. There’s no longer a fee to apply, and Child Maintenance Options offers free help working out which route suits you.

The three ways maintenance can be arranged

• Family-based arrangement: parents agree privately, with full flexibility, but it’s not legally enforceable unless converted into a court order.
• Child Maintenance Service (CMS): a statutory calculation and, if needed, collection service, used when parents can’t agree between themselves.
• Consent order: child maintenance terms included as part of a divorce financial settlement - this prevents either parent applying to the CMS for one year from the date of the order.

The CMS formula, step by step

The CMS calculates maintenance based on the paying parent’s gross weekly income (before tax and National Insurance, but after pension contributions), typically sourced directly from HMRC records:

• Basic rate (income £200-£800/week): 12% for one child, 16% for two children, 19% for three or more.
• Basic plus rate (income £800-£3,000/week): 12%/16%/19% on the first £800, plus 9%/12%/15% on income above £800.
• Reduced rate (income £100-£200/week): a lower calculation applies on income in this band.
• Flat rate (income £7-£100/week, or receiving certain benefits): £7 a week.
• Nil rate: no maintenance due if income is below £7 a week (and in certain other circumstances, such as being a student or in prison).
• The CMS only calculates on income up to £156,000 a year (£3,000/week) - for higher earners, the receiving parent can apply to court for additional ‘top-up’ maintenance under Schedule 1 of the Children Act 1989.

How shared care (overnight stays) reduces the amount

If the child stays overnight with the paying parent regularly - as set out in a Child Arrangements Order or informal agreement - the calculated amount is reduced based on the average number of nights per year:

• 52-103 nights a year: reduced by one-seventh
• 104-155 nights a year: reduced by two-sevenths
• 156-174 nights a year: reduced by three-sevenths
• 175+ nights a year (broadly equal care): reduced by half, plus a further £7 a week per child - this can bring the amount close to nil, though equal overnight care doesn’t automatically mean no maintenance is due, since the parents’ relative incomes still matter. Shared care can’t reduce the amount below £7 a week.

How other children the paying parent supports affect the calculation

If the paying parent has other children living with them, their gross income is reduced by 11%, 14% or 16% (for one, two, or three or more children) before the main calculation is applied. If they pay maintenance for children in more than one household, the total amount is split between those cases - so each individual arrangement can be lower than the headline percentage might suggest.

Direct Pay vs Collect & Pay

• Direct Pay: the CMS calculates the amount, but parents arrange the actual payment between themselves - no ongoing collection fees.
• Collect & Pay: the CMS collects from the paying parent and passes it to the receiving parent - this attracts collection fees, added on top for the paying parent and deducted from what the receiving parent gets, making it more expensive for both parties than Direct Pay when it can be avoided. The fees are currently 20% for the paying parent and 4% for the receiving parent.
• Changes are coming: the government has confirmed that Direct Pay will be abolished, with all CMS cases moving to Collect & Pay and fees cut to 2% for parents who pay reliably (20% will still apply to paying parents who don’t), with changes expected from 2027-28 - check GOV.UK for the latest position.

What child maintenance doesn’t cover

CMS-calculated maintenance is intended for everyday living costs - housing, food, clothing, basic education - and specifically doesn’t cover private school fees, university costs, or significant extracurricular expenses, which aren’t covered by the CMS calculation but can be agreed between parents or, in some cases, ordered by a court.

If you suspect income is being understated

The CMS primarily relies on HMRC income data, making it hard to hide standard employment income - but self-employed income, based on the most recent tax return, is more easily disputed. If you genuinely believe a paying parent is hiding income or arranging their affairs specifically to reduce maintenance, this is worth raising directly with the CMS (which can investigate) or seeking legal advice on a variation application.

The bottom line

Child maintenance follows a specific, calculable CMS formula based on gross income, number of children, shared care nights, and other dependants - understanding the actual mechanics, rather than relying on assumptions, helps both paying and receiving parents sanity-check whatever figure they’re working with, or whether a family-based arrangement or consent order might suit their situation better than the standard CMS route.