How the calculator works
This calculator uses the same formula as the UK Child Maintenance Service (CMS) to estimate weekly, monthly, and yearly maintenance payments.
What it calculates
The calculator considers:
- Gross income – the paying parent’s income before tax (but after workplace pension deductions)
- Number of children – how many children maintenance is being paid for
- Other children – children living with the paying parent (reduces the calculation)
- Shared care – nights the children spend with the paying parent (52+ nights reduces payment)
- Benefits – whether the paying parent receives income-based benefits
CMS rate bands
The Child Maintenance Service uses five rate bands:
| Rate | Weekly income | How it’s calculated |
|---|---|---|
| Nil rate | Under £7 or on certain benefits | No maintenance payable |
| Flat rate | £7 to £100 | £7 per week (fixed) |
| Reduced rate | £100 to £200 | £7 plus 17-31% of income over £100 |
| Basic rate | £200 to £800 | 12-19% of gross income |
| Basic rate plus | £800 to £3,000 | Basic rate on first £800, plus 9-15% on the rest |
Percentages by number of children
| Children | Reduced rate | Basic rate | Basic plus |
|---|---|---|---|
| 1 child | 17% | 12% | 9% |
| 2 children | 25% | 16% | 12% |
| 3+ children | 31% | 19% | 15% |
Shared care reductions
If the children stay overnight with the paying parent regularly, the maintenance amount is reduced:
| Nights per year | Reduction |
|---|---|
| 0-51 nights | No reduction |
| 52-103 nights | 1/7 off |
| 104-155 nights | 2/7 off |
| 156-174 nights | 3/7 off |
| 175+ nights | Half minus £7 |
Important limitations
This is an estimate only
This calculator provides an estimate based on the standard CMS formula. The actual amount calculated by the Child Maintenance Service may be different because:
- They use HMRC tax data which may differ from your estimate
- There may be variations for special circumstances
- Your situation may have factors not covered by this calculator
For an official calculation, use the GOV.UK child maintenance calculator or contact the Child Maintenance Service.
What this calculator doesn’t cover
- Self-employed income (complex rules apply)
- Income over £3,000 per week (court application needed)
- Variations for special expenses or additional income
- Historical arrears calculations
- Multiple receiving parents
Next steps
If you’re setting up maintenance
- Try to agree privately first – you can use this calculator as a starting point for discussions
- Consider a family-based arrangement – no fees, flexible, but not legally enforceable
- Use the CMS if needed – they can calculate and collect payments (fees apply)
Useful contacts
- Child Maintenance Options: 0800 171 2345 (free advice before using CMS)
- Child Maintenance Service: 0800 171 2345
- GOV.UK: www.gov.uk/child-maintenance
Learn more about child maintenance
Understand your options for arranging child maintenance, including private agreements and using the CMS.
Child maintenance guide →