CMS variations — asking the Child Maintenance Service to look at other income

REVIEWED BY: Sean McNamara on 2026-08-30

The standard CMS calculation is based on the paying parent's taxable gross weekly income, as reported to HMRC. But income isn't always that simple — rental income, dividends, or money deliberately moved out of sight can distort the figure. A variation asks the CMS to take other income or circumstances into account. This guide sets out the official grounds and thresholds. It is general information, not legal advice.

Variation grounds — receiving parents

A receiving parent can ask the CMS to consider:

Unearned income — rental income from property or land, or dividends and interest from savings and investments. This must be at least £2,500 a year to count
Notional income from assets — where the paying parent owns assets worth £31,250 or more, the CMS can calculate income the assets could produce and take that into account (for example, where someone lives off savings or property while reporting a low taxable income)
Diversion of income — where the paying parent controls the level of their taxable income by diverting it to another person or purpose, so the CMS figure doesn't reflect their real resources
Earned income while on benefits — if the paying parent gets benefits (paying the flat rate) but also has gross income from a pension, employment or self-employment of at least £100 a week

Variation grounds — paying parents

A paying parent can ask the CMS to consider special expenses — significant, specific costs that reduce their capacity to pay. These can include:

Costs of keeping in contact with the child — for example long-distance travel for contact, or overnight accommodation to enable contact
Debts from the relationship treated as prioritised debts (such as a mortgage on the former family home)
Costs of supporting a child with a disability or additional needs
Costs of repaying student loans

There are caps and evidence requirements; the CMS decides each case on its facts. You cannot rely on general living costs, new family living expenses, or ordinary debts that aren't connected to the child or the former relationship.

How to apply

1. Contact the CMS and ask for a variation — you can do this by phone or through your online account 2. Set out which ground you rely on and provide evidence (land registry records, bank statements, company filings, evidence of the other parent's assets) 3. The CMS investigates. If it accepts the variation, it recalculates and backdates to the date of the application 4. If you disagree with the variation decision, you can ask for a mandatory reconsideration, then appeal to the First-tier Tribunal (Social Security and Child Support) if needed

Practical notes

The paying parent cannot use a variation to count new family living expenses — the courts and the CMS have deliberately excluded this
Variations can be applied for by either parent at any time while a case is open
If you suspect hidden income, gather evidence before applying — tribunal cases show that well-documented applications succeed far more often than bare assertions
Annual review will not automatically pick up diversion or asset income — you usually need to ask

Official links

YourFamilyCase.co.uk is an independent information directory — we are not affiliated with, endorsed by, or connected to the DWP, the Child Maintenance Service, or gov.uk. This page is general information and is not legal advice.

Content verified against the official HMCTS court directory, gov.uk forms and fees pages, and the professional body registers (SRA, FMC, Bar Council). Last reviewed September 2026.