Maintenance estimator

Estimate a CMS calculation and see every step of the working, including other children, shared care and collection fees.

Private by design: this tool runs in your browser. Nothing you enter is sent to CMS Hub or stored on our server.

How the estimator works

It follows the 2012 scheme rules used by the CMS in England, Wales and Scotland: gross weekly income, the rate for that income, the reduction for other children, then the shared care reduction. The full method is explained in how the calculation works.

What it does not cover

  • Variations for special expenses or additional income
  • More than one receiving parent, where the amount is split between them
  • Children partly in local authority care
  • Default maintenance decisions when income is not known
  • Who should be the paying parent where care is equal. See equal care.

Check against your letter

If your CMS letter gives a different figure, compare it with the steps shown here. The difference usually comes from the income figure, the number of nights or the number of other children.

This is information, not legal advice. It explains how the system generally works in England, Wales and Scotland. Your situation may be different. Check the official guidance on GOV.UK and get free advice from the organisations on our Get help page before making important decisions.