Child Maintenance (CMS) Calculator

The Child Maintenance Service (CMS) calculates payments based on the paying parent's gross weekly income. The basic rates are 12% for one child, 16% for two children and 19% for three or more children. Income is usually sourced directly from HMRC tax data rather than from figures either parent supplies, which is why the number the CMS works from can feel out of date. This calculator follows the same formula to estimate weekly and monthly maintenance before the adjustments below are applied.

Income is read in bands. Nothing is due below £7 a week, the nil rate. From £7 to £100 a week, or where the paying parent gets certain benefits, a flat rate of £7 a week applies however many children are involved. Between £100 and £200 the reduced rate is £7 plus 17%, 25% or 31% of the income above £100 for one, two or three or more children, a little less where other children live with the paying parent. From £200 upwards the basic percentages take over, with a lower additional rate of 9%, 12% or 15% on the slice of income above £800 a week. Income above £3,000 a week is ignored altogether. Where a paying parent earns beyond what the formula covers, the receiving parent has to apply to the family court for a top-up order.

Two adjustments then pull the figure down. The gross income figure is reduced if the paying parent has other children living with them, by 11% for one, 14% for two and 16% for three or more, and stepchildren in the household count towards that. Shared overnight care reduces the liability afterwards. One night a week on average, meaning 52 to 103 nights a year, takes off one-seventh. Between 104 and 155 nights removes two-sevenths, 156 to 174 nights removes three-sevenths, and 175 nights or more halves the liability and takes a further £7 a week off for each child.

Only certain money counts as income. The CMS looks at gross weekly income for the latest HMRC tax year, covering PAYE earnings, self-employment profit, pensions and some benefits. Capital such as savings and property is left out unless it produces income, and neither a new spouse's earnings nor Child Benefit are included. Because the figure is historic, a parent whose income has moved by 25% or more can ask for a review. Unearned income from rent or dividends of £2,500 a year or more can be brought in, but only if the receiving parent tells the CMS about it. A parent living in a country with no reciprocal arrangement is beyond the CMS altogether, though the REMO scheme reaches some Commonwealth and EU states.

Collection is a separate choice from calculation. Direct Pay costs nothing, because the CMS works out the amount and the parents arrange payment between themselves, which is what most families do. Collect & Pay adds a 20% surcharge for the paying parent and a 4% deduction from the receiving parent, and it exists for cases with unreliable payments, a history of avoidance or an abusive ex-partner. If arrears build up, the CMS can order a deduction from earnings, take money straight from a bank account, send bailiffs, suspend a driving licence or passport for up to 2 years, and in rare cases push for a prison sentence.

Plenty of real costs sit outside the formula. Private school fees, music lessons and other extracurricular activities, dental and optical bills, private medical care, holidays and university maintenance are all absent from the CMS calculation, so parents have to agree them privately or go to court. A family-based agreement can cover any of this, but it is only legally binding once recorded as a court consent order, which costs a £62 court fee plus solicitor charges of roughly £300 to £1,500. Verbal and email agreements cannot be enforced, although courts give them some weight. Many separated parents run a family-based agreement for day-to-day money alongside a court order for specific items.

Maintenance runs until the child's 16th birthday, or until 20 if they stay in approved full-time education such as A-levels or a vocational course up to NVQ Level 3. Degrees do not count, and neither do apprenticeships paid by an employer, so payments stop when university starts. Marriage, joining the armed forces or going to prison also end the liability. If the paying parent dies, ongoing maintenance stops but arrears can be claimed against the estate. A new child in the paying parent's household triggers a recalculation that usually reduces the existing award, while the receiving parent remarrying changes nothing.