Child Maintenance Calculator

Q: What are the Collect & Pay fees?

CMS Collect & Pay charges the paying parent a 20% surcharge on top of the maintenance amount, and deducts 4% from the receiving parent's payment. For example, on £80/week maintenance the payer pays £96 and the receiver gets £76.80. Direct Pay is free — CMS calculates the amount but you arrange payments yourselves.

Q: What if my income changes?

CMS reviews calculations annually using updated HMRC income data. If your income changes by 25% or more, you can request an immediate reassessment. Changes in circumstances such as having another child or changing jobs can also trigger a review. Contact CMS directly to report changes.

Q: Can I appeal a CMS decision?

Yes. You can request a mandatory reconsideration within 30 days of a CMS decision. If you still disagree after reconsideration, you can appeal to a tribunal (HM Courts & Tribunals Service). You can also apply for a variation if the standard calculation does not reflect the true situation, such as hidden income or high travel costs for contact.

Calculate child maintenance using CMS 2025/26 rates. See how shared care, other children, and Collect & Pay fees affect your payments. Based on Child Maintenance Service/GOV.UK rates.

Calculate child maintenance using CMS 2025/26 rates

Gross weekly income

Before tax. CMS uses HMRC data to verify.

Number of qualifying children

Children the maintenance is for

Shared care nights per year

Overnight stays with paying parent. 52 = 1 night/week

Other children in paying parent's household

Children living with the payer (not qualifying children)

—

Try another scenario

How to Use This Calculator

CMS Calculation tab

Enter the paying parent's gross weekly income (before tax), the number of qualifying children, and shared care nights per year. The calculator applies the correct CMS rate band and shared care reduction to show weekly, monthly, and annual maintenance. Expand "More options" to account for other children living in the paying parent's household.

Collect & Pay vs Direct Pay tab

Enter the weekly maintenance amount from your CMS calculation. The calculator shows the true cost of using CMS Collect & Pay (20% surcharge on the payer, 4% deduction from the receiver) compared to making payments directly for free. See the annual cost difference to decide which arrangement works best.

Other Children Adjustment tab

If the paying parent has other children in their household (biological, adopted, or step-children they support), CMS reduces their income before calculating maintenance. This tab shows the exact impact: maintenance with and without the other children adjustment, so you can see the difference clearly.

Share your result

Every input is encoded in the URL. Click Share to send your exact scenario to a solicitor, mediator, or save it for later.

The Formula

CMS child maintenance uses a tiered system based on gross weekly income:

Rate bands (2025/26):
Nil rate: income ≤ £7/week → £0
Flat rate: £7.01–£100/week → £7/week
Reduced rate: £100.01–£199.99/week → £7 + taper
Basic rate: £200–£3,000/week → income × rate

Basic rate percentages:
1 child: 12% • 2 children: 16% • 3+ children: 19%

Other children reduction (applied to income first):
1 other child: 11% • 2: 14% • 3+: 16%

Shared care reduction (by overnight stays/year):
52–103 nights: 1/7 off • 104–155: 2/7 off
156–174: 3/7 off • 175+: 50% off + £7 reduction

Collect & Pay fees:
Payer: +20% surcharge • Receiver: −4% deduction

The CMS uses HMRC data to determine gross income. For employed parents, this is typically gross pay from the latest tax year. For self-employed parents, CMS uses the latest Self Assessment tax return. Income from benefits (except those specifically excluded) counts towards the calculation.

Example

Mark — earns £500/week gross, 2 children with ex-partner, shared care 52 nights/year

Mark earns £500 per week gross. He has 2 qualifying children from his previous relationship. The children stay with him one night per week (52 nights/year). He has no other children in his household.

CMS Calculation tab

Gross weekly income£500

Qualifying children2

Shared care nights/year52

Other children0

Rate bandBasic rate

Rate applied (2 children)16%

Basic weekly amount£80.00

Shared care reduction (1/7)−£11.43

Weekly maintenance£68.57

Monthly maintenance£297

Annual maintenance£3,566

Mark's basic rate is 16% of £500 = £80/week. With 52 shared care nights, he gets a 1/7 reduction, bringing his weekly payment to £68.57. If he used Collect & Pay instead of Direct Pay, he would pay an extra 20% (£13.71/week), costing him £713 more per year.

FAQ

How is child maintenance calculated by the CMS? ▼

The Child Maintenance Service (CMS) calculates maintenance based on the paying parent's gross weekly income, verified through HMRC records. The rate depends on income: nil rate (£7 or less), flat rate (£7.01–£100 = £7/week), reduced rate (£100.01–£199.99), or basic rate (£200–£3,000). For the basic rate, CMS applies 12% for 1 child, 16% for 2 children, or 19% for 3 or more children. If the paying parent has other children in their household, income is reduced by 11%–16% before the rate is applied.

How does shared care affect child maintenance? ▼

If the child regularly stays overnight with the paying parent, CMS reduces the maintenance amount. The reduction depends on the number of nights per year: 52–103 nights = 1/7 off, 104–155 nights = 2/7 off, 156–174 nights = 3/7 off, and 175+ nights = 50% off plus a further £7 reduction per week. Fewer than 52 nights per year means no shared care reduction applies. Both parents must agree on the number of overnight stays, or CMS will make a decision based on evidence.

What are the Collect & Pay fees? ▼

If you use the CMS Collect & Pay service (where CMS collects money from the payer and passes it to the receiver), the paying parent pays a 20% surcharge on top of the maintenance amount, and the receiving parent has 4% deducted from their payment. For example, on £80/week maintenance: the payer pays £96, and the receiver gets £76.80. Direct Pay is free — CMS calculates the amount but you arrange payments yourselves. There is a one-off £20 application fee to use CMS (waived for domestic abuse cases).

What if my income changes? ▼

CMS reviews maintenance calculations annually using updated HMRC income data. If your income changes by 25% or more at any time, you can request an immediate reassessment. Changes in circumstances — such as having another child, changing jobs, or the child moving — can also trigger a review. Contact the CMS directly to report changes. If you are self-employed, your maintenance is based on your latest Self Assessment tax return, so it updates when HMRC processes your return.

Can I appeal a CMS decision? ▼

Yes. If you disagree with a CMS decision, you can request a mandatory reconsideration within 30 days. CMS will review the decision and explain the outcome. If you still disagree after reconsideration, you can appeal to a tribunal (HM Courts & Tribunals Service). Common grounds for appeal include incorrect income figures, disputed shared care arrangements, or special expenses not being considered. You can also apply for a variation if you believe the standard calculation does not reflect the true situation (e.g., the paying parent has hidden income or high travel costs for contact).

Related Calculators

Add This Calculator to Your Website

Embed the sum.money Child Maintenance Calculator on your site. Free, responsive, always up-to-date.