How is Child Maintenance Calculated UK? Complete Guide 2026

How Child Maintenance is Calculated in the UK

Child maintenance helps ensure that children receive financial support from both parents after separation. The Child Maintenance Service (CMS) uses a specific formula to calculate payments.

The Basic Calculation

CMS calculates child maintenance based on the paying parent's gross weekly income:

Basic Rate Percentages

For the Basic Rate (income £200-£800 per week):

• 1 child: 12% of gross income
• 2 children: 16% of gross income
• 3+ children: 19% of gross income

Basic Plus Rate

For income £800-£3,000 per week:

• 1 child: 12% on first £800 + 9% on remainder
• 2 children: 16% on first £800 + 12% on remainder
• 3+ children: 19% on first £800 + 15% on remainder

Reductions Applied

The amount can be reduced for:

Shared Care

If the paying parent has the child overnight:

• 52-103 nights per year: 1/7 reduction
• 104-155 nights per year: 2/7 reduction
• 156-174 nights per year: 3/7 reduction
• 175+ nights per year: 1/2 reduction plus £7 per week

Other Children in the Household

If the paying parent has other children in their household, deductions are made before calculating the rate.

Example Calculation

Let's say a paying parent earns £40,000 per year (£769 per week gross) with 2 children and no overnight stays:

• Income: £769 per week
• Rate: Basic rate at 16%
• Calculation: £769 × 16% = £123.04 per week
• Monthly equivalent: approximately £533 per month

What Income is Included?

CMS uses HMRC data to determine income. This includes:

• Employment income (PAYE)
• Self-employment profits
• Pension income
• Some benefits and allowances

What If Income is Hidden?

If you believe the other parent is hiding income:

• Request a 'variation' from CMS
• Provide evidence of lifestyle inconsistent with declared income
• CMS can investigate assets and lifestyle

Private Agreements

You can make a 'family-based arrangement' instead of using CMS:

• No fees involved
• More flexible
• Requires cooperation
• Not legally enforceable unless made into a court order

CMS Fees

• Application fee: £20
• Collect and Pay service: 20% added to paying parent's amount, 4% deducted from receiving parent

Get Advice

If you need help understanding child maintenance or want to dispute a calculation, contact MCR Solicitors on 0161 466 1280.