How is child maintenance calculated by the Child Maintenance Service (CMS)?
Last updated: 10/04/2025
Want to find out how child maintenance is calculated by the CMS? After you apply for child maintenance the Child Maintenance Service will contact your child’s other parent or HM Revenue & Customs for details of their income.
CMS Contact Details
Child Maintenance Service 21
Mail Handling Site A
Wolverhampton
WV98 2BU
Telephone: 0800 171 2345
Relay UK: 18001 then 0800 171 2345
Monday to Friday, 8.30am to 3.30pm
Calls are free from mobiles and landlines.
After you apply for child maintenance, the Child Maintenance Service will contact your child’s other parent to ask for details about their circumstances and income. They may also contact HM Revenue & Customs if your child’s other parent does not reply or they need more information. The Child Maintenance Service will calculate how much child maintenance you should get based on this.
There are certain things which affect a paying parent’s income that will be taken into account by the Child Maintenance Service when calculating child maintenance payments. These include payments into pension schemes, certain costs or expenses and the number of other children your child’s other parent pays maintenance for.
If the paying parent is a student any earnings from employment will be used to calculate child maintenance payments. Student finance, including loans and grants, will not count for child maintenance.
Child maintenance is reviewed each year. Payments may be affected by changes in the paying parent’s circumstances, such as a change in their income or family. The Child Maintenance Service should be told about these changes as soon as possible.
Child maintenance rates
Child maintenance rates are applied to gross weekly income. The rates differ depending on the gross weekly income amount:
Best evidence assessment
If the Child Maintenance Service do not get the information they need to calculate the maintenance payment they can either make a “best evidence assessment” or a “default maintenance decision”.
A best evidence assessment uses previous information held about a paying parent’s gross income to work out the amount of child maintenance that must be paid.
Default maintenance decision
A default maintenance decision is made where there is no information about the paying parent’s income. It is a fixed amount based on the number of children the paying parent must pay child maintenance for.
The default rates are:
£39 a week for one child
£51 a week for two children
£64 a week for three or more children
Basic rate
The basic rate applies if the paying parent’s gross weekly income is between £200 and £800. The child maintenance payment will be a percentage of the paying parent’s income.
The following percentages of gross weekly income will apply:
12% for one qualifying child
16% for two qualifying children
19% for three or more qualifying children
If the paying parent’s gross weekly income is over £800 per week, the basic rate will be used for the first £800 and a ‘basic plus’ rate for income over £800 per week.
Gross income over £3000 per week will not be included by the Child Maintenance Service in the child maintenance calculation.
Call Child Maintenance Options for more information:-
Telephone: 0800 953 0191 (Mon – Fri, 8am – 8pm)
Reduced rate
A reduced rate is used where the paying parent’s gross weekly income is more than £100 but less than £200.
The reduced rate has two parts:
- an amount equal to the flat rate of £7 per week plus
- a percentage of the gross weekly income above £100 per week
The percentages are:
17% for one qualifying child
25% for two qualifying children
31% for three or more qualifying children
Example
If a paying parent’s income is £110 per week and there is one qualifying child, the child maintenance payment would be:-
The flat rate of £7 plus 17% of £10 (the weekly income over £100)
£7 + £1.70 = £8.70
Flat rate
If the paying parent’s gross weekly income is £100 per week or less, or if they receive an income based benefit, a flat rate is used for child maintenance.
The flat rate is a £7 per week regardless of the number of children.
Nil rate
No child maintenance is payable if the paying parent is:
- a person with a gross weekly income of less than £7
- a child under 16 or a young person under 19 who is in full-time non-advanced education (up to A-level or equivalent)
- a person who is aged 16 or 17 and getting income support or income-based jobseeker’s allowance
- a young person getting a work-based training allowance
- a prisoner
- in residential care or a nursing home and getting help with fees or on certain benefits
- a patient in hospital who has had their benefits reduced
Reductions for other children
If your child’s other parent is paying maintenance for children from another relationship the amount of maintenance you receive will be reduced.
If your children’s other parent has a child from another relationship living with them (a relevant child) this will also reduce your maintenance payments.
If you do not agree with the child maintenance calculation
If you think your child maintenance calculation is wrong you can ask for a revision, supersession, variation or can appeal. Which one you ask for depends on what you think is wrong.
Find out more about challenging a decision from the CMS.
If the paying parent lives abroad
If your child’s other parent lives abroad you can still use the Child Maintenance Service if your child’s other parent is:
- a UK civil servant or works within Her Majesty’s Diplomatic Service
- a member of the armed forces
- working for a company that is based and registered in the UK
- working on secondment for a UK regional health authority or local council
If your child’s other parent does not fit into one of these you can ask the Scottish Government for advice by emailing, phoning or writing to them at:
Email: maintenanceenforcement@gov.scot
Telephone: 0131 244 2417 or 0131 244 4829
Fax: 0131 244 4848
The Scottish Government Justice Directorate
Central Authority and International Law Team
St Andrew’s House
Regent Road
Edinburgh
EH1 3DG