Finance⏱ 6 min read
How to Calculate Child Maintenance Payments in the UK
The Child Maintenance Service uses a specific formula that most parents find opaque. Here's exactly how payments are calculated — including income bands, shared care reductions, and the flat rate.
Child maintenance is one of the most contested financial calculations in family law. The Child Maintenance Service (CMS) applies a formula — but few people know the details. Here's the complete picture.
Who Pays and Who Receives
The "paying parent" is the one who doesn't live with the child (the non-resident parent). The "receiving parent" is the main carer. The CMS calculates what the paying parent should contribute based primarily on their gross weekly income.
The Five Rate Tiers
Rate TypeGross Weekly IncomeCalculation
Nil rateBelow £7/week (£364/year)No payment due
Flat rate£7–£100/week or on certain benefits£7/week flat
Reduced rate£100–£200/weekSliding scale formula
Basic rate£200–£3,000/week% of gross income (see below)
Basic rate plusAbove £3,000/weekBasic rate + extra % on excess
Basic Rate Percentages
Basic rate (gross weekly income £200–£3,000):
1 child: 12% of gross weekly income
2 children: 16% of gross weekly income
3+ children: 19% of gross weekly income
Example: paying parent earns £600/week gross
1 child: £600 × 12% = £72/week
2 children: £600 × 16% = £96/week
3 children: £600 × 19% = £114/week
Gross Weekly Income Calculation
Gross weekly income = Annual gross income ÷ 52
Annual gross income comes from HMRC records.
The CMS uses income from 2 tax years ago as the starting point,
then updates if current income has changed by more than 25%.
If employed: PAYE gross salary
If self-employed: gross profit from self-assessment
Pension income: included
Benefits: mostly excluded (except some)
Shared Care Reduction
If the paying parent has overnight stays with the child, maintenance is reduced:
Nights per Year with Paying ParentReduction Applied
0–51 nights (less than 1/7)No reduction
52–103 nights (about 1 night/week)Reduce by 1/7
104–155 nights (~2 nights/week)Reduce by 2/7
156–174 nights (~3 nights/week)Reduce by 3/7
175+ nights (equal or near-equal)Reduce by 50% (half and half)
Example: basic rate payment £72/week, 104 nights shared care
Reduction = 2/7 × £72 = £20.57
Adjusted payment = £72 − £20.57 = £51.43/week
Multiple Children in Different Families
If the paying parent has children with a previous partner and is also paying for them, the basic rate percentage is reduced for children in the second family:
If paying parent already has:
1 other child: divide basic rate by 1.1 before applying
2 other children: divide by 1.2
3+ other children: divide by 1.3
This prevents double-counting obligations across families.
The Direct Pay vs Collect and Pay Distinction
CMS offers two service levels: "Direct Pay" where parents manage transfers themselves (free) and "Collect and Pay" where CMS enforces and transfers payments (CMS charges 20% on top from the paying parent and deducts 4% from the receiving parent). Use Direct Pay unless there's a history of non-payment.