Shared Care Child Maintenance Calculator

What this calculator does

If you pay child maintenance through the Child Maintenance Service (CMS) and your child stays overnight with you, those overnight stays – known as shared care – reduce how much you pay. This Shared Care Child Maintenance Calculator works out your basic-rate payment for 2026/27 and then applies the correct overnight-stays reduction, so you can see exactly what you should be paying each week, month and year.

It is built for paying parents (and receiving parents who want to check a figure) who already have, or expect, a CMS arrangement and want to understand how nights spent with the child change the bill. Enter the number of children, your gross weekly income and the number of nights the children stay with you each year – the tool does the rest using the official CMS bands. The base CMS rate uses 12%, 16% or 19% of gross weekly income for 1, 2 or 3+ children, then shared care knocks off 1/7, 2/7, 3/7 or half depending on how many nights you have the children. It is a guidance estimate; the CMS makes the legally binding decision.

How it works

The calculator follows the CMS basic-rate formula and then applies the shared-care reduction:

1. Basic rate. On gross weekly income up to £800 you pay 12% (1 child), 16% (2 children) or 19% (3+ children). On any income between £800.01 and £3,000 a week, a lower top-up rate of 9%, 12% or 15% applies. Income over £3,000/week is ignored.
2. Shared care reduction. The number of nights the child stays with you each year sets a reduction band:
   • 52 to 103 nights → reduce by 1/7 (14.29%)
   • 104 to 155 nights → reduce by 2/7 (28.57%)
   • 156 to 174 nights → reduce by 3/7 (42.86%)
   • 175 nights or more → halve the amount, then deduct a further £7 per child per week
3. £7 weekly floor. Once a reduction is applied, the amount normally cannot fall below £7 a week.

Worked example

Imagine a paying parent with 2 children, a gross weekly income of £600, and the children stay overnight 104 nights a year.

• Basic rate for 2 children = 16% of £600 = £96.00 per week (income is under £800, so no top-up rate).
• 104 nights falls in the 104–155 band, a 2/7 (28.57%) reduction: £96.00 × (1 − 2/7) = £68.57 per week.
• That works out at about £297.14 per month (£68.57 × 52 ÷ 12) and £3,565.71 per year.

If the same parent had the children for 175+ nights instead, the £96.00 would be halved to £48.00 and then reduced by a further £7 per child (£14), leaving £34.00 per week.

Frequently asked questions

How many overnight stays do I need to reduce my child maintenance?

You need at least 52 nights a year (an average of one night a week) before any shared-care reduction applies. Below 52 nights there is no reduction. From 52 nights the reduction rises in bands – 1/7, 2/7, 3/7 and then half at 175+ nights.

What happens at 175 nights or more?

At 175 or more nights a year the basic amount is halved, and then a further £7 per child per week is deducted. So for two children you would lose an extra £14 a week on top of the 50% cut.

Is there a minimum I have to pay?

Yes. Once a shared-care reduction is applied, the weekly amount normally cannot drop below £7 a week. Very low earners (income of £7 to £100 a week, or on certain benefits) usually pay the flat rate of £7 a week instead of the basic rate.

Does this calculator give the official CMS figure?

It uses the same published CMS basic-rate percentages and shared-care bands, so it is a close estimate. The Child Maintenance Service makes the legally binding calculation and may also account for other children, benefits and special circumstances.

Source & further reading

Rates and shared-care bands are taken from the official UK government guidance: How child maintenance is worked out – GOV.UK.

Related tools on UK Calculator: Child Maintenance Calculator, Salary Calculator, Take-Home Pay Calculator, Child Benefit Calculator, and all UK calculators.