CSA Calculator UK (2026)
The Child Support Agency (CSA) has been replaced by the Child Maintenance Service (CMS), but the calculation works in a similar way. Use our free calculator to get your estimate using the current formula.
CSA Is Now the CMS
The Child Support Agency (CSA) closed in 2012 and all cases transferred to the Child Maintenance Service (CMS). If you're looking for a "CSA calculator", you need the current CMS calculator, which is what we provide below.
The key difference: the CMS uses gross income (before tax) instead of net income, and has updated rate bands.
Current Child Maintenance Rates (Formerly CSA Rates)
The CMS calculates maintenance as a percentage of the paying parent's gross weekly income:
Example Monthly Amounts
| Salary | 1 Child | 2 Children | 3 Children |
|---|---|---|---|
| £20,000 | £200/m | £267/m | £317/m |
| £30,000 | £300/m | £400/m | £475/m |
| £40,000 | £400/m | £533/m | £633/m |
| £50,000 | £500/m | £667/m | £792/m |
| £60,000 | £578/m | £787/m | £946/m |
See the full table for all salary levels
CSA vs CMS: What Changed?
| Feature | Old CSA | Current CMS |
|---|---|---|
| Income Used | Net income (after tax) | Gross income (before tax) |
| Income Source | Self-declared | HMRC tax records |
| Rates (1 child) | 15% of net income | 12% of gross income |
| Rates (2 children) | 20% of net income | 16% of gross income |
| Rates (3+ children) | 25% of net income | 19% of gross income |
| Collection Fee | Free | 20% surcharge (paying parent) + 4% (receiving parent) |
Calculate Using the Current Formula
Our calculator uses the official 2026 CMS rates, with adjustments for shared care, pensions, and other children.
Frequently Asked Questions
Is the CSA calculator still available?
The original CSA calculator is no longer available as the agency closed in 2012. Our calculator uses the current CMS formula which replaced the CSA system. The rates and calculation method have been updated but work in a similar way.
What happened to my old CSA case?
All CSA cases were closed between 2012 and 2019. If your case was still active, you were contacted by the CMS to set up a new arrangement. If you weren't contacted and need to arrange maintenance, you can apply to the CMS or make a private arrangement.
Am I paying more or less under the CMS than the old CSA?
It depends on your circumstances. The CMS uses gross income which is higher than net income, but the percentage rates are lower. For most people, the actual amounts are broadly similar. Use our free calculator to check your current amount.
Do I have to use the CMS or can I arrange it privately?
You can make a private "family-based arrangement" which avoids CMS fees. Many parents use a calculator like ours to agree a fair amount, then arrange payments directly. Compare CMS vs private arrangements