What does the Child Maintenance (CMS) Calculator do?

Calculate child maintenance using CMS rules. Accounts for income, shared care nights and other children. All calculations are performed in your browser using official UK rates and thresholds.

Are benefit amounts accurate?

This calculator uses the published 2025/26 benefit rates. However, actual entitlements depend on a full assessment by the Department for Work and Pensions (DWP) and may differ from estimates.

How do I claim this benefit?

You can apply for most benefits through GOV.UK or your local Jobcentre Plus. Some benefits require an online application; others may require a phone call or paper form.

Child Maintenance (CMS) Calculator

Calculate child maintenance using CMS rules. Accounts for income, shared care nights and other children.

Last updated: April 2026 · Source: GOV.UK — Calculate child maintenance

Gross Weekly Income

Children to Pay For

Shared Care Nights/Week

Other Children in Household

Weekly Child Maintenance

£72.00

£312.00/month · £3,744.00/year

Based on CMS basic rate (12% for 1 child).

Gross income under £7/week = nil rate. £7-£100 = flat rate (£7/week). Over £800/week = reduced rate on excess.

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

The Child Maintenance Service (CMS) calculates payments based on the paying parent's gross weekly income. The basic rates are: 12% for one child, 16% for two children and 19% for three or more children. Income is usually sourced directly from HMRC tax data.

The gross income figure is reduced if the paying parent has other children living with them (11% for one, 14% for two, 16% for three or more). Shared overnight care also reduces the amount: one night per week on average reduces the liability by one-seventh.

If income is above £3,532 per week, the reduced rate tiers apply to the portion above this threshold. For very low incomes (below £200/week), a flat rate of £7 per week applies. This calculator follows the CMS formula to estimate weekly and monthly maintenance.

Example: Two children, £600/week gross income

Gross weekly income: £600
Rate for two children: 16%
Weekly maintenance: £600 × 16% = £96
Monthly equivalent: £96 × 52 ÷ 12 = £416
With one overnight per week: reduced by 1/7 = £82.29/week (£356.60/month)

Source: GOV.UK — Calculate child maintenance

Frequently Asked Questions

What does the Child Maintenance (CMS) Calculator do?: Calculate child maintenance using CMS rules. Accounts for income, shared care nights and other children. All calculations are performed in your browser using official UK rates and thresholds.
Are benefit amounts accurate?: This calculator uses the published 2025/26 benefit rates. However, actual entitlements depend on a full assessment by the Department for Work and Pensions (DWP) and may differ from estimates.
How do I claim this benefit?: You can apply for most benefits through GOV.UK or your local Jobcentre Plus. Some benefits require an online application; others may require a phone call or paper form.