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In the most recent statistics, which cover the 2019/20 financial year, the Department for Work and Pensions (DWP) estimated that there were around 2.4 million separated families in the UK, and 3.6 million children living in such families. Around 44% of these families were estimated to have no child maintenance arrangement. The Child Maintenance Service (CMS), which provides a statutory maintenance scheme, was estimated to be the sole organiser of maintenance for around 15% of separated families.

This briefing describes how the CMS calculates child maintenance under the 2012 Child Maintenance Scheme in Great Britain. Section 10 describes the similar, but separate, scheme in Northern Ireland.

Sections 7-9 set out policy debates on the 2012 child maintenance system and changes compared to the 1993 and 2003 schemes. This includes the decision to remove the “lifestyle inconsistent with income” ground for variation, the requirement of the person with care to estimate the unearned income of the non-resident parent, and analysis on the impact of child maintenance on poverty.

Information on the collection and enforcement of maintenance is available in the Library Briefing Child Maintenance: Fees, enforcement and arrears.


The Child Maintenance Service has said that it is moving towards “a full service” and stated that they “will take action if child maintenance is not paid”. They have advised the parent with care to “keep a record of any payments you receive and any missed payments. If any payments are missed or not made in full, we may begin collection activity to recover any unpaid child maintenance”.

In January 2021, the DWP said the CMS is “reviewing all non-paying cases to make sure that each one is up to date, with outstanding changes, actions and arrears and balances being corrected”. As of 23 March 2021, the CMS Direct page says “if any payments are missed, we will review your case and may begin collection activity to recover any unpaid child maintenance”. The CMS in Northern Ireland may not be able pursue arrears during the Coronavirus period and calculations of liability may be delayed.

Calculating child maintenance

There are five rates of maintenance that a non-resident parent can be required to pay, depending on their financial circumstances and, in some cases, those of their new partner (see Section 3 and Annex 1 for more information).

The CMS uses gross weekly income to calculate maintenance due. Gross weekly income is defined as income before any deductions for income tax and national insurance but after any contributions to approved personal or occupational pension schemes. Income information is either supplied to the CMS from Her Majesty’s Revenue and Customs (HMRC) or from the non-resident parent.

If the non-resident parent’s gross weekly income is above £3,000, the person with care can apply to the court for additional maintenance.

For certain rates, the CMS calculation also takes account of the number of children the non-resident parent must pay child maintenance for and the average number of nights of shared care a week (where the child stays overnight with the non-resident parent).

Maintenance is reviewed each year, but parents should inform the CMS of changes in circumstances. The CMS booklet, How we work out child maintenance, provides a step-by-step guide to the calculation process. In large part, Sections 3 to 6 and Annex 1 of this briefing summarises the guidance. It should not, however, be considered a substitute for it when looking for detailed advice on specific cases. The CMS has also published a series of factsheets on applying for, managing, calculating and enforcing maintenance arrangements.

In cases where “special expenses” are incurred by the non-resident parent (such as fuel costs when travelling to a child’s home) or the non-resident parent gains “additional income” which is not captured by the HMRC (for example, “unearned” income from rents or savings), a request for variation can be made. These are described in Section 6.

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