Child Maintenance Calculator 2026/27 - CMS Formula
The CMS formula uses the paying parent's gross annual income and applies a percentage based on the number of children: 12% for 1 child, 16% for 2 children, 19% for 3+. On a £35,000 salary with 1 child and no overnight stays, that's about £81/week (£350/month). Overnight stays reduce payments. 156+ nights halves the payment.
Figures verified against HMRC 2026/27 rates on .
Written by James HartleyCIMA
Calculator
Gross income before tax. CMS uses HMRC data. Includes salary, self-employment, rental income.
Reduces payment proportionally
Income is reduced before calculating if paying parent has other children
Estimated Monthly Payment
£350
£80.77/week · £4,200/year
How This Is Calculated
Direct Pay
£350/month
No CMS fee · Both parents agree
Collect & Pay (CMS)
£364/month
+4% payer · Receiver gets £336
You can agree maintenance directly with the other parent (family-based arrangement) to avoid the 4% CMS collection fee. A direct arrangement is free and more flexible.
These insights are generated based on your inputs and general UK financial guidelines. They do not constitute personal financial advice. Always consult a CIMA-qualified accountant or FCA-regulated adviser before making financial decisions.
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How Child Maintenance Calculator 2026/27 - CMS Formula Works
The CMS statutory formula
Child Maintenance Service payments are based on the paying parent's gross weekly income. The base rate is 12% for 1 child, 16% for 2, and 19% for 3+. If the paying parent has other children from another relationship, gross income is reduced first before the rate is applied.
Overnight stay reductions
If the paying parent has the children overnight regularly, the payment is reduced: 1 to 52 nights (1/7th reduction), 53 to 104 nights (2/7ths), 105 to 155 nights (3/7ths), and 156+ nights (50% reduction).
Direct Pay vs Collect & Pay
Parents can arrange payments directly (Direct Pay, no CMS fee). If CMS collects and forwards payment, a fee applies: the paying parent pays 4% extra, and the receiving parent receives 4% less. Collect and Pay should be a last resort.
Frequently Asked Questions
The CMS uses the paying parent's gross income (from HMRC data) and applies a percentage: 12% for 1 child, 16% for 2, 19% for 3+. Overnight stays reduce the payment. If the paying parent also supports other children, income is adjusted downwards first.
The CMS uses gross income from HMRC, including salary, self-employment profits, pension income, and rental income. They can request information for the previous tax year. It's updated annually or if income changes by more than 25%.
Yes. Parents can reach a private family-based arrangement without involving the CMS. This can be more flexible but is not legally enforceable. If the arrangement breaks down, either parent can apply to CMS. Direct Pay arrangements made through CMS are also possible.
The CMS formula applies to gross income up to £156,000 per year. For income above this, the receiving parent must apply to court for a 'top-up' order. The standard formula still applies for the first £156,000.
Related Guides
Child Benefit UK 2026/27: Rates and Who Can Claim
Weekly Child Benefit rates, eligibility, how to apply, and the High Income Child Benefit Charge.
Read guideChild Maintenance Calculations: How the CMS Formula Works
A step-by-step walkthrough of the CMS statutory formula, income adjustments, and overnight stay reductions.
Read guideAverage UK Salary 2025: Complete Breakdown by Age, Region and Industry
Understanding median UK salaries helps contextualise typical child maintenance amounts.
Read guideWas this calculator helpful?
Official Rates Used
This calculator uses official HMRC rates for 2026/27. View the current rates at GOV.UK:
Rates last verified:
Disclaimer: This calculator provides estimates based on standard HMRC rates for 2026/27. Results may vary based on individual circumstances. This is not financial advice. Always consult a qualified accountant or CIMA-qualified financial adviser for personal tax matters.