Frequently Asked Questions
Everything you need to know about child maintenance calculations
How accurate is this calculator?
Our calculator uses the exact same formula as the Child Maintenance Service (CMS). It accounts for income bands, shared care arrangements, other children in the household, and pension deductions. The calculation is based on the official CMS guidelines.
Is my data safe?
Yes, all calculations happen locally in your browser. We do not store, transmit, or have access to your personal or financial information. Your data never leaves your device during the calculation.
What income should I enter?
Enter your gross annual income - this is your total income before tax and National Insurance. Include salary, bonuses, and regular overtime. If self-employed, use your taxable profit. Do not include benefits like Universal Credit or Child Benefit.
What counts as a shared care night?
A shared care night is when the child stays overnight with the paying parent. This includes regular overnight stays, holiday periods, and any other overnight arrangements. Count the total nights per year.
How do other children affect the calculation?
If you have other children living in your household (not the ones in this maintenance arrangement), the CMS reduces your net income before calculating maintenance. This is 11% for 1 other child, 14% for 2, and 16% for 3 or more.
What are the different rate types?
The CMS uses different rates based on weekly income: Nil Rate (below £7/week), Flat Rate (£7-£100/week pays £7), Reduced Rate (£100-£199/week sliding scale), Basic Rate (£200-£800/week pays 12-19%), and Basic Plus (over £800/week pays additional 9-15% on excess).
How does shared care reduce maintenance?
The more nights the paying parent has the child, the less maintenance they pay. 52-103 nights reduces by 1/7 (14.3%), 104-155 nights by 2/7 (28.6%), 156-174 nights by 3/7 (42.9%), and 175+ nights by 50% minus £7 per child.
What is included in the PDF reports?
The Basic Report (£4.99) includes your calculation breakdown, date stamp, and reference ID. The Comprehensive Report (£9.99) adds income change scenarios (+/-10%, +/-25%), shared care variations, and an 18-year payment projection.
Is this an official CMS document?
No, our reports are for reference and planning purposes only. They are not official CMS documents. For official assessments, you must contact the Child Maintenance Service directly.
How often is maintenance reviewed?
The CMS typically reviews cases annually or when there is a significant change in circumstances (income change of 25% or more, change in shared care, etc.). Our calculator provides a point-in-time estimate.
Do I need to use the CMS?
No, parents can make their own private arrangements (family-based arrangements). The CMS is one option if you cannot agree. Our calculator helps you understand what the CMS formula would produce.
What if I have multiple children with different parents?
You would need to do separate calculations for each arrangement. The "other children in household" field accounts for children living with you from other relationships.