Child Maintenance Calculator
Estimate UK child maintenance under the CMS 2012 scheme from gross income, children and shared care nights.
An estimate using the Child Maintenance Service's 2012 scheme rules. Only the CMS can make a binding calculation, and it uses HMRC income figures that may differ from what you enter here.
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What is this?
A Child Maintenance Calculator (CMS Calculator) estimates how much child maintenance a paying parent owes under the UK Child Maintenance Service's 2012 statutory scheme. It is the formula used when separated parents cannot agree a family-based arrangement themselves.
How to Use the Child Maintenance Calculator
This CMS calculator estimates child maintenance under the UK Child Maintenance Service's 2012 scheme - the statutory formula used when parents cannot agree an arrangement between themselves.
The calculation runs in six steps: work out gross weekly income, deduct pension contributions, reduce it for other children in the paying parent's household, apply the rate band, apply any shared-care reduction for overnight stays, then convert to a weekly, monthly or yearly figure.
1. Enter the Paying Parent's Gross Income
Enter gross income - before tax, after pension - as a yearly, monthly or weekly figure. The CMS uses the gross annual income HMRC holds for the most recent tax year, so your own figure may differ slightly from theirs.
2. Add Pension Contributions
Private pension contributions are deducted from gross income at step 2. Leave this blank if there are none.
3. Set the Number of Children
Choose how many children maintenance is being paid for. Rates are banded at one, two, and three or more, so a fourth child does not raise the percentage further.
4. Declare Other Children in the Household
Children the paying parent supports in their own home reduce gross weekly income before the rate is applied - by 11% for one, 14% for two and 16% for three or more.
5. Choose the Shared Care Band
Enter how many nights a year the children stay overnight with the paying parent. From 52 nights the liability falls by a seventh, rising to half above 175 nights plus a further £7 a week for each child.
Key Formulas Used in the Calculator
Basic Rate (£200 to £800 a week)
Maintenance=Gross Weekly Income×⎩⎨⎧12%16%19%
Twelve percent for one child, 16% for two, and 19% for three or more. On £600 a week with two children that is 16% of £600, or £96 a week.
Reduced Rate (£100.01 to £199.99 a week)
Maintenance=£7+(Income−£100)×⎩⎨⎧17%25%31%
The £7 flat amount is charged on the first £100, then a percentage on the rest. On £150 a week with one child that is £7 + 17% of £50, or £15.50 a week.
Basic Plus Rate (£800.01 to £3,000 a week)
Maintenance=£800×⎩⎨⎧12%16%19%+(Income−£800)×⎩⎨⎧9%12%15%
The lower percentage applies only to income above £800. On £1,000 a week with two children that is 16% of £800 plus 12% of £200, or £152 a week. Income above £3,000 a week is outside the formula.
Shared Care Reduction
Reduction=⎩⎨⎧71,72,73,21+£7 per child,52–103 nights104–155 nights156–174 nights175+ nights
The reduction comes off the calculated liability. Above 175 nights the amount halves and a further £7 a week is removed for each child.
Benefits
Implements the official CMS 2012 scheme rules from gov.uk
Covers all five rates including the basic plus band above £800 a week
Applies the £3,000 weekly income cap and explains the top-up route
Uses the correct reduced rate of £7 plus a percentage of income above £100
Applies shared care as sevenths, with the extra £7 a child above 175 nights
Accepts income yearly, monthly or weekly
Shows all six calculation steps with the numbers filled in
When & Where to Use
Estimating a liability before applying to the CMS
Checking whether a CMS assessment looks right
Working out the effect of a change in income
Seeing how extra overnight stays change the amount
Understanding the effect of a new child in the household
Comparing a private family-based arrangement with the statutory figure
Budgeting for maintenance payments after separation
Who Should Use This Calculator
The Child Maintenance Calculator is for separated parents in the UK - whether paying or receiving - along with family solicitors, mediators and advisers who need a quick estimate of the statutory figure.
Tips to Get the Best Deal
Gross income means before tax but after pension contributions
The rate bands stop at three children - a fourth adds nothing to the percentage
Only overnight stays count towards shared care, not daytime contact
Income above £3,000 a week needs a court application for any top-up
The CMS charges fees for collection that this figure does not include
A change of 25% or more in income can trigger a reassessment mid-year
Parents who agree a family-based arrangement are not bound by this figure
Frequently Asked Questions (FAQs)
How is child maintenance calculated in the UK?
The CMS takes the paying parent's gross weekly income, deducts pension contributions, reduces it for other children in their household, then applies a percentage based on the income band and number of children. Shared care then reduces the result.
What percentage of income is child maintenance?
On the basic rate, which covers £200 to £800 gross a week, it is 12% for one child, 16% for two and 19% for three or more. Above £800 a week those percentages still apply to the first £800, with 9%, 12% or 15% on the income above it.
How does shared care reduce child maintenance?
From 52 nights a year the liability falls by a seventh, from 104 nights by two sevenths, from 156 nights by three sevenths, and above 175 nights by half plus a further £7 a week for each child.
Do other children in my household reduce what I pay?
Yes. Gross weekly income is reduced by 11% for one other child, 14% for two, and 16% for three or more before the maintenance rate is applied.
What happens if income is over £3,000 a week?
The formula caps at £3,000 gross a week. The receiving parent can apply to the court for a top-up order covering income above that figure.
What is the flat rate?
£7 a week. It applies when gross weekly income is between £7 and £100, or when the paying parent receives certain benefits such as Income Support, JSA, ESA or the State Pension.
Is this calculator official?
No. It follows the published CMS rules but is an estimate. Only the Child Maintenance Service can make a binding calculation, and it uses HMRC income figures.
Pro Tips
Gross income means before tax but after pension contributions.
Rate bands stop at three children - a fourth adds nothing to the percentage.
Only overnight stays count towards shared care, not daytime contact.
Income above £3,000 gross a week needs a court application for any top-up.
The CMS uses HMRC income data, which may differ from the figure you enter.
Only the Child Maintenance Service can make a binding calculation.