For EY-Parthenon, prepare to explain why a strategic proposal creates value and what evidence could overturn that view. A growing market, an attractive target or an exciting technology is a starting point. The case becomes useful when you connect it to the client’s economics and ability to execute.
I would practise finding the assumption on which the recommendation depends. Then calculate how strong that assumption needs to be and decide what you would investigate first.
Read the team name as carefully as the firm name
EY expanded the EY-Parthenon brand across its Strategy and Transactions service line in 2025. That means a role under the brand may involve strategy, transactions, corporate finance or a more specialised team. Start with the responsibilities in the vacancy.
A strategy candidate should practise open business problems. A valuation or transaction-execution candidate should also prepare the technical and operating decisions relevant to that role. Use the invitation to establish whether the next task is a case conversation, technical discussion, presentation or another assessment.
This is a useful preparation choice, not administrative housekeeping. It determines where your next hour of practice should go.
Learn from a published strategy case
EY-Parthenon Strategy in Australia publishes an electricity-generation investment example. It asks candidates to connect demand, supply, prices and investment, then think about uncertainty and whether to commit now or preserve the ability to invest later.
The lesson is to connect the pieces. Demand growth can attract competitors. More supply can change prices. A project that looks attractive in isolation may be less attractive once you consider those responses.
Attempt the questions before reading the suggested reasoning. Then ask yourself which assumption you treated as fixed even though another participant could change it.
Separate the target from the buyer’s plan
Consider an original acquisition exercise. A software company is evaluating a target. The price is £400,000 above the buyer’s estimate of the target’s standalone value. Management argues that selling the buyer’s product to the target’s customers will justify this premium.
The proposed cross-selling programme has these assumptions:
| Input | Assumption |
|---|---|
| Eligible target customers | 1,000 |
| Customers who buy the additional product | 20% |
| Annual revenue per converted customer | £2,000 |
| Contribution margin before programme support | 80% |
| Annual additional support cost | £80,000 |
| One-time integration cost | £300,000 |
| Evaluation period | Three years |
Assume conversion occurs at the start, converted customers stay for all three years and there are no other benefits or costs. These simplified figures let us test the cross-selling claim; they are not a complete acquisition valuation.
First keep the components separate: standalone value, buyer-specific benefit and the cost of capturing that benefit. Otherwise the same improvement can accidentally appear in both the target valuation and the synergy estimate.
Calculate the value claim
At 20% conversion, 200 customers buy the additional product. Annual contribution before support is 200 × £2,000 × 80% = £320,000. After £80,000 of support, annual incremental benefit is £240,000.
Across three years, that is £720,000 before discounting and tax. The premium plus integration spending totals £700,000, leaving just £20,000 on this simplified undiscounted comparison.
That is a thin cushion. The proposal depends on the full conversion assumption, prompt delivery and continued retention. You would not describe £720,000 of benefits without also explaining the £700,000 commitment needed to obtain them.
Quick Case Math Drill
A facilities-services group is buying a pest-control firm and plans to sell pest control to its own office clients after the deal.
- Existing office clients
- 500
- Contribution per buyer
- £3,000 a year
- Premium plus integration
- £900,000
Over three undiscounted years, what conversion rate just recovers the premium and integration cost?
Find the assumption worth testing first
If conversion is 15%, annual contribution before support falls to £240,000. After support it is £160,000, or £480,000 across three years. The same premium and integration spending now exceed the benefits by £220,000.
The three-year undiscounted break-even conversion is about 19.6%:
[£700,000 ÷ 3 + £80,000] ÷ [1,000 × £2,000 × 80%].
The management forecast of 20% sits only slightly above that threshold. I would therefore prioritise evidence of customer eligibility and willingness to buy over polishing an already detailed integration timetable.
Ask how the forecast was built. Are the 1,000 customers distinct and reachable? Do they need the product? Who controls the buying decision? Will contracts and permissions allow the proposed sales approach? Have comparable customers actually purchased, or only expressed interest?
Those questions turn “synergies are risky” into a focused diligence plan.
Follow the cost of execution
A customer who wants the product may still need integration, onboarding and support. If the £80,000 support estimate excludes work needed to serve the new customers, the benefit is overstated.
EY-Parthenon’s M&A service description spans diligence through execution and integration. For preparation, use that connection: a value claim should survive the operating work required to deliver it.
Name the dependency that matters most. In this exercise it might be access to compatible customer data, the sales team’s capacity or a product integration needed before selling can begin. A six-month delay in benefits would materially change a proposal with only £20,000 of undiscounted headroom.
Quick Structuring Drill
A payroll software company is buying a small time-tracking app and plans to sell it to existing payroll customers.
- Customer pilot
- 30% of trial users bought the app
- Selling can start
- Once both products share one login
- Engineering team
- Also committed to a tax-rule update
Which evidence should the deal team test first to protect the synergy?
Give a point of view before asking for everything
A useful recommendation is: “I would not justify the £400,000 premium on this cross-selling forecast yet. The simplified three-year benefit only just covers the premium and integration cost, and conversion below roughly 19.6% removes that cushion. I would validate eligible demand and delivery cost before revising the valuation.”
You can still examine other reasons to buy the target. Keep them separate and evidence-backed. If the acquisition is attractive without cross-selling, say why. If management must reduce the price to make it work, quantify the issue instead of adding vague strategic benefits.
Practise a change of view
Ask a partner to alter one assumption: conversion, retention, integration cost or launch timing. Update the value comparison and explain whether the same diligence priority remains most important.
Prepare experience examples alongside cases, especially occasions when you changed a plan after finding contrary evidence. Be ready to explain your own contribution and reasoning.
Use the M&A framework to connect standalone value, buyer-specific benefits and execution costs. Then apply the approach to a different acquisition or investment decision, so you are practising judgment rather than remembering this calculation.
Frequently asked questions
Understanding which EY-Parthenon role you face
Does an EY-Parthenon role always mean strategy consulting?
No. In 2025, EY expanded the EY-Parthenon brand across its Strategy and Transactions service line. A role under that name may therefore involve strategy, transactions, corporate finance or a more specialised team. Read the responsibilities in the vacancy before deciding how to prepare, rather than relying on the brand name alone.
How should a valuation or transaction candidate prepare differently?
Prepare the technical and operating decisions relevant to the role, as well as open business problems. A strategy candidate can concentrate on unstructured questions about growth or value. A valuation or transaction-execution candidate should add the specific judgements that role involves. Check the vacancy's responsibilities and build your practice around them.
What is the main lesson of EY-Parthenon's published electricity-generation case?
Connect the parts rather than analysing each in isolation. The example, published by EY-Parthenon Strategy in Australia, asks candidates to link demand, supply, prices and investment. It then asks them to consider uncertainty and whether to commit now or preserve the ability to invest later. Timing and flexibility can matter as much as a project's headline appeal.
Why might a growing market still be a poor investment?
Because growth invites a response. Rising demand can attract competitors, and the extra supply they add can push prices down. A project that looks attractive in isolation may be less attractive once you account for what others are likely to do. Ask how prices behave after new capacity arrives, not just how fast demand grows.
Testing an acquisition's value claim
Why separate the target's standalone value from the buyer's plan?
Because the premium pays for buyer-specific benefits. In the example, the price is £400,000 above the buyer's estimate of the target's standalone value, and management relies on cross-selling to justify that difference. Keeping the two apart shows which assumptions must hold for the extra payment to make sense, instead of blending them into one optimistic valuation.
How much value does the cross-selling plan create in the example?
At 20% conversion, 200 of 1,000 eligible customers buy. Contribution is 200 × £2,000 × 80%, or £320,000 a year. After £80,000 of support, that falls to £240,000, or £720,000 over three years. The premium plus integration spending totals £700,000, which leaves a cushion of only £20,000.
Does the £20,000 cushion account for discounting and tax?
No. It is a simplified comparison, undiscounted and before tax. The premium is paid at the deal, but the benefits arrive over three years, so discounting would reduce their present value and could erase the cushion. Mention this limitation when you present the numbers to show you know the simple figure flatters the deal.
What conversion rate does the deal need to break even?
About 19.6% over three years, undiscounted. Divide the £700,000 cost by three and add the £80,000 annual support. Then divide by the contribution available if every eligible customer bought: 1,000 × £2,000 × 80%. Management's 20% forecast sits only slightly above that threshold, so test conversion first.
What happens to the deal if conversion is 15% instead of 20%?
The value claim fails. Contribution before support drops to £240,000, or £160,000 after support, which gives £480,000 over three years. Against £700,000 of premium and integration spending, the benefits fall short by £220,000. A five-point miss turns a thin gain into a substantial loss, which shows how sensitive the case is.
Why does the support cost estimate matter so much?
A customer who wants the product may still need integration, onboarding and support. If the £80,000 estimate excludes work needed to serve the new customers, the benefit is overstated. With such a thin cushion, even a modest underestimate matters. A value claim should survive the operating work required to deliver it, from diligence through integration.
Presenting and revising your view
How do I give a recommendation before I have all the data?
State a provisional view and the evidence that would change it. For example, say you would not justify the £400,000 premium on this forecast yet. The benefit barely covers the costs, and conversion below roughly 19.6% removes the cushion. Then say you would validate eligible demand and delivery cost before revising the valuation.
Can I still support the acquisition for reasons other than cross-selling?
Yes, but keep those reasons separate and evidence-backed. Rejecting cross-selling as a justification for the premium does not mean the target lacks strategic value. Present each rationale with its own assumptions so the interviewer can test each claim independently. This also stops vaguer benefits from quietly propping up a weak cross-selling forecast.
How should I practise updating my view mid-case?
Ask a partner to change one assumption, such as conversion, retention, integration cost or launch timing. Recalculate the value comparison and explain whether the same diligence priority still matters most. Alongside cases, prepare examples of times you changed a plan after finding contrary evidence, and be clear about your own contribution and reasoning.