Child Maintenance Calculations in the UK: CMS Rates and How to Challenge Assessments

Child Maintenance Calculations in the UK: Child maintenance is really important for families in the United Kingdom. It is what helps kids get the money they need when their parents are not together anymore. The Child Maintenance Service is the group that usually helps with this. They decide how much money one parent should give to the parent. The Child Maintenance Service (CMS) looks at a lot of things to make this decision, such, as how money each parent makes and how much time each parent spends with the child. The Child Maintenance Service does a lot of work to make sure kids get the child maintenance they need.

But let’s be honest, the way CMS works isn’t always simple. Plenty of parents complain that the calculations feel off, sometimes out of date or just plain unfair. This is especially true if someone’s self-employed, gets bonuses, or splits care more evenly. In this guide, you’ll find out how CMS actually works, what the latest payment rates look like, and what you can do if you think they’ve made a mistake with your case.

Contents

1. What Is Child Maintenance in the UK?
2. What Is the Child Maintenance Service (CMS)?
3. How Child Maintenance Is Calculated in the UK
4. Current CMS Child Maintenance Rates
5. Shared Care and Its Impact on Payments
6. When CMS Calculations Can Change
7. Common Problems With CMS Assessments
8. How to Challenge a CMS Decision
9. Mandatory Reconsideration in the UK
10. Appealing to an Independent Tribunal
11. When to Seek Legal Advice
12. Final Thoughts

Child Maintenance Calculations in the UK:

What Is Child Maintenance in the UK?

When parents are not together anymore one parent has to help the parent by paying something called child maintenance. This money is used to pay for the childs things, like a place to live food to eat clothes to wear and things they need for school. It also helps pay for things the child likes to do. Child maintenance is very important because it helps make sure the child has everything they need.

In the United Kingdom child maintenance usually applies when:

• My parents live in homes. They do not live together in the house. My parents have their separate places.
• The child usually stays with one of their parents. This parent takes care of the child most of the time. The child lives mainly with one parent. That parent is, in charge of them.
• There is no private financial agreement in placeParents can agree on payments privately, but when agreement is not possible, the Child Maintenance Service (CMS) can calculate and manage payments.

What Is the Child Maintenance Service (CMS)?

The Child Maintenance Service is the government department responsible for:

• Calculating child maintenance payments

• Reviewing and updating assessments

• Enforcing unpaid child maintenance

CMS replaced the former Child Support Agency (CSA) and uses a standard formula designed to be consistent and income-based. CMS does not decide custody or contact arrangements—only financial support.

How Child Maintenance Is Calculated in the UK

CMS calculations are primarily based on the gross weekly income of the paying parent. This income information is usually taken directly from HM Revenue & Customs (HMRC).

Key Factors Used by CMS

Gross Weekly Income

CMS considers:

• Employment income

• Bonuses and commission

• Certain pension contributions

For self-employed parents, income is based on tax returns submitted to HMRC.

Number of Children

The number of children covered by the application directly affects the percentage of income used.

Other Children

If the paying parent supports other children living with them, CMS may reduce their assessable income before calculating payments.

Shared Care Arrangements

If the child stays overnight with the paying parent, payments may be reduced depending on the number of nights per year.

Current CMS Child Maintenance Rates (UK)

CMS applies different rates depending on income level.

Nil Rate

Applies if:

• Gross weekly income is under £7

• The paying parent is under 16

• The paying parent is in prison

Flat Rate – £7 per week

Applies when income is between £7 and £100 per week, or if the paying parent receives certain benefits.

Reduced Rate

Applies when income is between £100 and £200 per week, using a combination of flat and percentage-based calculations.

Basic Rate (Most Common in the UK)

For gross weekly income between £200 and £800:

• One child: 12%

• Two children: 16%

• Three or more children: 19%

For income above £800 (up to £3,000 per week), a lower percentage applies to the remaining amount.

Shared Care and Its Impact on Payments

Shared care can reduce child maintenance payments, depending on the number of overnight stays per year.

Typical reductions apply when:

• The child stays at least 52 nights per year with the paying parent

• Evidence of shared care is provided

Shared care disputes are common and often form the basis of CMS challenges.

When CMS Calculations Can Change

CMS assessments are reviewed automatically once a year, but they can also change if circumstances change, such as:

• Job loss or reduced income

• Pay increases or bonuses

• Changes in self-employment income

• New children in either household

• Changes to shared care arrangements

Failing to report changes promptly can lead to arrears or enforcement action.

Common Problems With CMS Assessments

Parents frequently challenge CMS decisions due to:

• Outdated HMRC income data

• Self-employed income not accurately reflected

• Undeclared bonuses or additional income

• Incorrect shared care assumptions

• Delays in updating income changes

These issues can result in unfair payment amounts.

How to Challenge a CMS Decision

If you believe a CMS assessment is wrong, you have the legal right to challenge it.

Step 1: Request a Mandatory Reconsideration

A Mandatory Reconsideration (MR) is the first step in challenging a CMS decision.

You must:

• Request it within 30 days of the decision

• Contact CMS by phone or in writing

During this process, CMS will review the calculation using any new evidence you provide.

Mandatory Reconsideration in the UK

To improve your chances, provide clear evidence such as:

• Recent payslips

• HMRC tax returns

• Proof of shared care arrangements

• Evidence of other dependent children

CMS may confirm, change, or partially adjust the original decision.

Appealing to an Independent Tribunal

If you disagree with the Mandatory Reconsideration outcome, you can appeal to an independent tribunal.

Key points:

• Appeals must be lodged within one month

• The tribunal is independent of CMS

• Decisions are legally binding

Tribunals can order CMS to recalculate payments or reconsider specific factors.

When to Seek Legal Advice

While many parents manage CMS challenges on their own, legal advice may be helpful if:

• Income is complex or inconsistent

• A parent is suspected of hiding income

• Significant arrears or enforcement action exists

• Multiple children or households are involved

Family law solicitors experienced in child maintenance cases can help protect your rights.

Final Thoughts

Child maintenance in the United Kingdom is supposed to be fair. The thing is, mistakes happen and people disagree about it a lot. If you want to make sure the money is right you need to know how the CMS rates, how calculations work. You have to understand how they do the calculations for child maintenance. It is also good to know how to challenge the decision if you think it is not right. This way the payments for child maintenance will be correct and fair, for everyone involved with child maintenance.

If something seems wrong, act quickly. Request a Mandatory Reconsideration, gather evidence, and seek legal advice where necessary. A fair child maintenance assessment benefits not only parents but, most importantly, the child.

Sources & Further Reading

• UK Government – Child Maintenance Service
  https://www.gov.uk/child-maintenance-service
  (Official CMS guidance on how child maintenance works in the UK)

• GOV.UK – Calculate Child Maintenance
  https://www.gov.uk/calculate-child-maintenance
  (Official child maintenance calculator and rate explanations)

• Citizens Advice – Challenging Child Maintenance Decisions
  https://www.citizensadvice.org.uk/family/children-and-young-people/child-maintenance/
  (Independent guidance on disputes, mandatory reconsideration, and appeals)