For family lawyers advising high-net-worth clients, the concept of “top-up” child maintenance is often one of the most contested elements in financial proceedings. The decision in James v Seymour [2023] EWHC 844 (Fam) adds further clarity (and complexity) to the landscape—reconciling parental affluence, fairness, and legislative boundaries.

But what exactly is a top-up order? And how far should the English courts go to ensure that a child’s lifestyle mirrors that of the richer parent?

What Is a “Top-Up” Order?

Under the Child Support Act 1991, the Child Maintenance Service (CMS) calculates maintenance obligations up to a gross annual income of £156,000. For earnings above this cap, the court regains jurisdiction under section 8(6), allowing it to make “top-up” orders. The rationale? In ultra-wealthy cases, CMS figures don’t touch the sides of the child’s actual needs or expectations.

James v Seymour: Conventional Awards vs Lifestyle Claims

In James v Seymour, the mother sought to increase maintenance to over £2,000 per month per child based on a “disparity of lifestyle” with the father, a successful private equity executive. But Mr Justice Mostyn wasn’t persuaded, stating:

“The amount that would be payable under the formula... is plainly excessive and not reasonably proportionate.”

Mostyn J preferred a conventional needs-based assessment, applying what he termed an “Adjusted Formula Methodology” (AFM) for high-income cases up to £650,000, acknowledging both its utility and its flaws.

CB v KB [2019]: Enter the Formula

This earlier case set the ball rolling. Mostyn J suggested that the CMS formula should provide a logical starting point—even for incomes up to £650,000. The so-called “Mostyn formula” offered predictability, but it was soon criticised for producing arbitrary per-child results and failing to reflect economies of scale in larger families.

Collardeau-Fuchs v Fuchs [2022]: Introducing HECSA

In Collardeau-Fuchs, the court made a crucial distinction between:

  • Conventional child support awards, calculated by reference to proportionate expenses.
  • Household Expenditure Child Support Awards (HECSAs), where the award reflects broader household running costs and lifestyle parity.

Top-up orders in HECSA cases go beyond food and clothing—they cover multiple properties, drivers, nannies, and international schooling. But such awards must still meet the fairness test under section 25 of the Matrimonial Causes Act 1973.

What Did James v Seymour Add?

Mostyn J’s most valuable contribution may be his proposed AFM framework, with adjustments based on:

  • School fees and other grossed-up costs;
  • Pension contributions;
  • Number of children and level of shared care.

This model aims to avoid disproportionate outcomes and offers guidance for incomes between £156,000 and £650,000.

He also acknowledged its limits:

  • It shouldn’t apply to variation applications;
  • It doesn’t work well for unearned income or capital-rich respondents;
  • It mustn’t override the discretionary test under s.25.

Practical Tips for Practitioners

  1. Budget First: A detailed child-focused budget remains the cornerstone of any claim. Don’t assume income alone drives quantum.
  2. HECSA or Not?: Be clear whether the claim is for a HECSA-style award (lifestyle parity) or a conventional needs-based sum.
  3. Use the AFM Sparingly: As a reference tool—not a rule.
  4. Don’t Overreach: Courts are alive to inflated claims. In James v Seymour, the court saw through attempts to use the father’s wealth as a blank cheque.
  5. Equalisation Isn't a Goal: Lifestyle parity may be a factor, but it's not the legal test. The court won’t iron out every disparity, particularly post-divorce.

Conclusion

In the HNW world, child maintenance can range from the modest to the majestic. But James v Seymour reminds us that fairness, not fortune, is the measure—and that clear, proportionate claims still carry the day. Practitioners should embrace the guidance while remembering that even in luxury, legal principles must still apply.