By Michelle Uppal, a matrimonial solicitor with 25 years’ experience and a partner at Lowry Legal in London, England.
The result of a Child Maintenance Service (CMS) assessment isn’t necessarily the final word. If your circumstances have changed since it originally took place, or you have come to believe an existing calculation doesn’t reflect financial reality, a child maintenance variation provides a formal route to challenge the figure.
This guide explains how variations work, who can apply, what grounds are available, and what to expect from the process. Whether you’re a paying parent facing an assessment that feels unfair, or a receiving parent who suspects the other side’s income is understated, knowing your options is the first crucial step.
What is a Child Maintenance Variation?
A CMS variation is a formal request to depart from the typical child maintenance calculation. It allows either parent to ask the CMS to use a different income figure, or to take into account complex factors the standard formula might ignore.
There are two types of CMS variation:
- An Increase Variation: Used by the receiving parent to argue that the paying parent’s true income is actually higher than the CMS calculation reflects.
- A Decrease Variation: Used by the paying parent to argue that the standard assessment is unfair given their specific circumstances.
It’s important to understand that variations are not granted automatically. The CMS must first be satisfied that there are valid grounds before it will consider departing from its standard assessment.
What Are the Grounds for a Child Maintenance Variation?
There are two categories: grounds to increase the assessment (most relevant to receiving parents) and grounds to decrease it (most relevant to paying parents). The CMS will only consider a variation if one of these recognised grounds applies.
Grounds to Increase Maintenance
These are most relevant to the person receiving payment; particularly where the paying parent is self-employed, a company director, or has significant, and complex, assets.
Additional income: Where the paying parent has income not captured by their HMRC tax return, such as overseas earnings, money paid to a third party, or payments received informally.
Diversion of income: Where income is being routed through a company, trust, or to a partner or family member specifically to reduce the apparent income figure. This is one of the most contested grounds in high net worth divorce cases, therefore it’s one of the most important to resolve.
Assets: Where the paying parent holds assets worth more than £31,250 (excluding their main home, pension, and the business they use to generate their declared income). The CMS can apply a notional income of 8% per year to the value of assets above this threshold.
Lifestyle inconsistency: Not a formal ground in itself, but often powerful supporting evidence. If a paying parent’s visible lifestyle — their property, vehicles, travel, and general spending — is clearly at odds with their declared income, this may strengthen the argument for a deeper investigation.
Grounds to Decrease Maintenance
These are most relevant to paying parents with specific financial pressures.
Special expenses: Certain costs can be used to reduce the maintenance figure. These include:
- The cost of maintaining contact with the child (travel expenses where significant).
- Costs relating to a child’s disability or long-term illness.
- Boarding school fees, in limited circumstances; where education costs are being met by the paying parent and this is agreed or ordered.
Note: day school fees and general private education costs are not covered by the standard CMS calculation at all. If school fees are a significant issue in your case, our full guide to divorce and school fees covers this in more detail.
Prior debts: Debts incurred before the child maintenance liability began may be considered in limited circumstances.
Costs of supporting a child in another household: If the paying parent has children from a second relationship, this may already be factored into the standard calculation. However, a variation can address specific additional costs that might not have been captured.
How Does the Variation Process Work?
Either parent can apply directly to the CMS at any time, and there is no fee to do so. Once your application is made, the process broadly follows these steps:
- Apply to the CMS: Either parent can request a variation at any time without charge.
- CMS Notification: Both parents are informed and given the opportunity to provide information.
- Information Gathering: The CMS may contact HMRC, request financial documentation, or ask questions of both parties.
- Decision: The CMS decides whether to apply the variation and, if agreed, recalculates their assessment accordingly.
- Mandatory Reconsideration and Appeal: If you disagree with the outcome, you can request a mandatory reconsideration, and thereafter appeal to the First-tier Tribunal.
The process can take up to three months to complete. In more complex cases, particularly those involving company structures or disputed income, it sometimes takes longer.
CMS Variation in Practice: An Illustrative Example
The following is a fictional example for illustration only. Outcomes will vary depending on individual circumstances.
A company director draws a salary of £60,000 per year and declares dividends of £20,000, making a total declared income of £80,000. On this basis, the CMS assesses child maintenance at around £185 per week for one child.
However, the company has retained profits of £350,000, and the director’s lifestyle — a huge family home, monthly international travel, and a lease on a new high-value vehicle, seems wholly inconsistent with an £80,000 income.
The receiving parent applies for a variation on grounds of income diversion. The CMS investigates and determines that a notional income should be attributed to the retained profits above the £31,250 threshold. The revised assessment increases maintenance significantly to account for this.
In this kind of case, early legal advice (and potentially a forensic accountant) can make a huge difference to the outcome. For a deeper look at how the CMS treats directors and business owners, see our guide: Child Maintenance for the Self-Employed and Business Owners.
When is a Court Order Better Than a CMS Variation?
For many high net worth families, a family court application can achieve more than a CMS variation. It is generally preferable when finances are complex, income is disputed, or the paying parent’s declared earnings don’t reflect their actual, day-to-day, wealth.
A top up application through Schedule 1 Children Act 1989 application to the family court may be more appropriate when:
- The paying parent’s income exceeds the CMS cap of £3,000 per week gross. In such cases, the court can award a top-up beyond what the CMS can order. See our guide: Child Maintenance Above the CMS Cap for more on this.
- Income is held in offshore structures, trusts, or across multiple forms that the CMS may struggle to unpick effectively.
- You need full financial disclosure, as the court can compel this in a way the CMS cannot.
- Your children’ s needs go beyond basic maintenance, encompassing school fees, extracurricular costs, and other special expenses that could be included in a court order.
A consent order agreed between parties can also provide more certainty — and closure — than an open CMS assessment, which remains subject to an annual review.
How Often Can Child Maintenance Be Modified?
CMS assessments are reviewed annually as standard. Either parent can also request a review, or apply for a variation, at any time if there has been a significant change in circumstances.
Common triggers include:
- A substantial change, either up or down, in the paying parent’s income.
- A business sale or significant financial windfall.
- A change in the number of nights the child spends with the paying parent.
- Either parent’s income has changed by 25% or more since the last assessment.
For paying parents who have genuinely seen their income fall, such as a self-employed parent whose business has struggled, a variation or review can reduce their liability fairly. Meanwhile, for receiving parents, a change in the paying parent’s financial position is valid grounds to push for an increase.
For context on how income is assessed in the first place, particularly for business owners and directors, our guides on CMS calculations for business owners, child maintenance and dividends, and child maintenance loopholes cover all the important details.
FAQs About CMS Variations
Does a variation affect backdated payments?
A variation generally takes effect from the date of the application, not retrospectively. If you believe an assessment is wrong, this is one of the main reasons to apply promptly.
Can both parents apply for a variation at the same time?
Yes, the CMS will consider both applications together and reach a single revised assessment.
Is a variation the same as a change of circumstances review?
No, they’re different processes. A change of circumstances review updates the income figure used in the standard CMS calculation. A variation asks the service to depart from the standard calculation altogether, on specific grounds.
Getting the Right Outcome with a CMS Variation
A child maintenance variation is less “secret loophole”, and more “well-established safeguard”. It exists solely to ensure that CMS assessments reflect lived-in financial reality, not just a low-end baseline declared to HMRC.
For receiving parents, this process is one of the most important tools available when a payer’s declared income doesn’t tally with how they live. On the flipside, it can also provide a legitimate route to a fair assessment when the standard formula produces an unreasonable result for the paying parent.
Whichever perspective most closely describes your own, getting the details right matters enormously. Lowry Legal is highly experienced in advising HNW clients across England and Wales on child maintenance disputes, variation applications, and Schedule 1 proceedings. We’re here to provide all the guidance you might need to get a fair outcome.
Contact us today to arrange a confidential conversation about your circumstances.
This article is intended as general guidance only and does not constitute legal advice. Child maintenance rules can change, and every case is different. Always seek specialist legal advice for your specific situation
