How does the Child Maintenance Service calculate child maintenance?

Last updated: 17/02/2021

After you apply for child maintenance the Child Maintenance Service will contact HM Revenue & Customs to find out the other parent’s income.

After you apply for child maintenance the Child Maintenance Service should contact HM Revenue & Customs to find out the other parent’s income. They will also contact the other parent to ask for details about their circumstances and will usually give a calculation of how much child maintenance will be payable, based on the information received from HM Revenue & Customs.

There are certain things which affect a paying parent’s income that can be considered by the Child Maintenance Service when calculating child maintenance payments. These include payments into pension schemes, certain costs or expenses the paying parent pays, and the number of other children who the paying parent supports.

If the paying parent is a student earnings from employment will be used to calculate child maintenance payments but students finance, including loans and grants, will not count.

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 circumstances. The Child Maintenance Service should be told about these changes as soon as possible.

If the paying parent, their employer, or accountant has not supplied gross income information to HM Revenue & Customs for use in making a child maintenance decision, the Child Maintenance Service can ask for this information.

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 an 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:

£38 a week for one child
£51 a week for two children
£61 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 £3000.

The following percentages of gross income will apply:

12% for one qualifying child
16% for two qualifying children
19% for three or more qualifying children

If the paying parents gross weekly income is over £3000 per week you can apply to the court for extra child maintenance.

Reduced rate

A reduced rate is applied to paying parents with a gross weekly income of more than £100 but less than £200.

The Reduced rate consists of two parts:

  • An amount equal to the flat rate. This currently stands at £7 per week plus
  • A percentage of the balance of gross weekly income above £100

The pecentages are:

17% for one qualifying child
25% for two qualifying children
31% for three or more qualifying children


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

For gross weekly income of £100 or less, or where a paying parent receives an income based benefit, a Flat rate of £7 applies, regardless of the number of qualifying children.

Nil rate

A Nil rate applies if the paying parent is under 16, under 19 and in full-time education, a prisoner or if the gross weekly income is less than the flat rate amount.


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

In certain circumstances you can ask for child maintenance to be recalculated if you have reason to believe it is not correct. This is called a variation. In most cases an application for a variation can be made over the phone, but if the application is complicated the Child Maintenance Service may ask you to apply in writing.

When you think you are not receiving enough maintenance

You can apply for a variation if you think the parent paying maintenance has other taxable income that wasn’t considered in the calculation. If the Child Maintenance Service can identify this extra income, it will be added to the other parent’s gross income and used to make a new calculation.

When maintenance can be reduced

The paying parent can apply for a variation to have their maintenance payments reduced if he/she has certain special expenses. These can include:

  • Contact costs
  • Costs of a long-term disability or illness of a “relevant child”
  • Debts of the relationship
  • Boarding school fees

If the paying parent lives abroad

If your child’s other parent lives abroad, you can’t use the Child Maintenance Service to arrange child maintenance unless 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.