LEK Consulting’s written case interview is the single most differentiating element in their hiring process — and the one most candidates underprepare for. Unlike the interactive case discussions at McKinsey or BCG, LEK hands you a 25–30 slide data packet and asks you to build a structured recommendation presentation from scratch. Based on our analysis of candidate outcomes, roughly 70% of final-round rejections trace back to weak written case performance rather than traditional case interview skills.
What the Written Case Actually Tests
The written case is not a harder version of a regular case interview. It evaluates a fundamentally different skill set — one that mirrors what LEK consultants do on day-one engagements.
| Skill | How It’s Tested | Why LEK Cares |
|---|---|---|
| Information triage | 30 slides of mixed-quality data, only ~40% directly relevant | Consultants must filter signal from noise in client data rooms |
| Structured synthesis | Complete 7 partially-filled outline slides with coherent analysis | Client deliverables require turning messy data into clean narratives |
| Quantitative reasoning | Populate blank charts, tables, and calculation worksheets | LEK’s strategy work is heavily numbers-driven |
| Executive communication | 20-min presentation + 10-min Q&A to a senior panel | Partners need consultants who can present confidently to C-suite clients |
| Time management | 60 minutes for analysis and slide completion | Real project deadlines don’t wait for perfect analysis |
The written case sits in LEK’s final round alongside two traditional case interviews. In our experience working with candidates, the written case carries disproportionate weight in the final decision — interviewers view it as the closest proxy to actual consulting work.
The Written Case Format: What You Receive
When you sit down for the written case, you receive two items:
1. The Data Packet (25–30 slides)
This contains a mix of:
- Client background and strategic situation (2–3 slides)
- Market data — size, growth rates, segmentation (4–6 slides)
- Competitive landscape — market shares, positioning, capabilities (3–5 slides)
- Financial data — P&L excerpts, cost breakdowns, margin analysis (4–6 slides)
- Customer or operational data — surveys, utilization metrics, quality indicators (3–5 slides)
- Qualitative information — management interview excerpts, industry expert quotes (2–3 slides)
2. The Outline Slides (approximately 7 slides)
These are partially completed presentation slides with:
- Headers indicating the expected topic for each slide
- Blank charts or tables you need to populate with your analysis
- Calculation worksheets where you show your quantitative work
- Space for your written conclusions and recommendations
The outline slides are your roadmap — they tell you exactly what LEK expects you to deliver. Candidates who ignore these and build their own structure almost always run out of time.
The 60-Minute Strategy
Time management separates strong candidates from rejected ones. Here is the approach that consistently produces the best results:
flowchart TD
A["Minutes 0–5<br/>Read Outline Slides First"] --> B["Minutes 5–10<br/>Skim Data Packet & Map to Slides"]
B --> C["Minutes 10–40<br/>Targeted Analysis & Slide Completion"]
C --> D["Minutes 40–52<br/>Build Narrative Arc"]
D --> E["Minutes 52–57<br/>Rehearse Key Transitions"]
E --> F["Minutes 57–60<br/>Final Math Check"]
style A fill:#e8f4e8,stroke:#2d7d2d
style C fill:#e8f0fe,stroke:#1a56db
style F fill:#fef3c7,stroke:#d97706
Minutes 0–5: Read the Outline Slides First
This is counterintuitive — most candidates dive straight into the data packet. Instead, start with the 7 outline slides. They reveal:
- The exact structure LEK expects
- Which analyses you need to perform
- What calculations are required
- The logical flow of the final presentation
Write a one-line note on each outline slide describing what data you need to find.
Minutes 5–10: Skim the Data Packet
Now flip through all 30 slides quickly — spend no more than 10–15 seconds per slide. Your goal is not to analyze anything yet. Instead:
- Mark each data slide with the outline slide number it supports
- Star the 3–4 slides that contain the most critical data
- Cross out slides that are clearly irrelevant to the outline
After this pass, you should have a clear map: “Data slide 8 feeds into outline slide 3.”
Minutes 10–40: Targeted Analysis and Slide Completion
This is the core analytical phase. Work through the outline slides in order, pulling data from the mapped packet slides. For each outline slide:
- Extract the relevant numbers from the data packet
- Calculate any required metrics (margins, growth rates, market shares)
- Populate the blank charts or tables on the outline slide
- Write 2–3 bullet points summarizing your key finding for that slide
Do not aim for perfection — directional accuracy matters more than decimal precision. If a calculation would take 8 minutes, estimate it in 2 minutes and move on.
Minutes 40–52: Build Your Narrative Arc
With all outline slides populated, step back and ensure they tell a coherent story. The strongest presentations follow this structure:
| Slide Position | Purpose | Example |
|---|---|---|
| Slide 1 | Situation summary and core question | “Client X is evaluating entry into the European biosimilars market” |
| Slides 2–4 | Key analyses supporting your recommendation | Market sizing, competitive dynamics, financial implications |
| Slides 5–6 | Synthesis and recommendation | “We recommend entering via acquisition of a mid-size player” |
| Slide 7 | Risks and next steps | Key assumptions to validate, implementation considerations |
Write a one-sentence transition between each slide. This becomes your speaking guide during the presentation.
Minutes 52–57: Rehearse Key Transitions
Quietly talk through the first two slides and the recommendation slide. You will not have time to rehearse the full presentation, so focus on:
- A confident opening that frames the problem in 30 seconds
- A clear recommendation statement you can deliver without reading
- Prepared responses to the most obvious challenge question
Minutes 57–60: Final Math Check
Scan your calculations for order-of-magnitude errors. A $50M market that you accidentally wrote as $500M will undermine your entire presentation. Check:
- Units (millions vs. billions, percentages vs. decimals)
- Direction (growth vs. decline, positive vs. negative margin)
- Internal consistency (do your numbers across slides add up?)
The 30-Minute Presentation
After your 60 minutes of preparation, you present to a panel of 2–3 LEK interviewers — typically a Partner and one or two Managers or Principals.
Presentation Phase (20 minutes)
Opening (2 minutes): State the client situation and your recommendation upfront. LEK interviewers — like all strategy consultants — prefer answer-first communication. Do not build suspense.
Body (15 minutes): Walk through your outline slides in order. For each slide:
- Lead with the “so what” — the key insight — before explaining the analysis
- Reference specific data points: “As shown in the market sizing on slide 3, the addressable market is approximately $2.4 billion”
- Acknowledge data limitations rather than pretending your analysis is bulletproof
Closing (3 minutes): Restate your recommendation, summarize the 2–3 strongest supporting arguments, and flag key risks or areas requiring further analysis.
Q&A Phase (10 minutes)
The Q&A tests whether you truly understand your analysis or merely assembled slides. Expect:
- Challenge questions: “What if the market growth is 3% instead of the 7% you assumed?” Be ready to explain how your recommendation changes — or doesn’t — under different assumptions.
- Omission probes: “I noticed you didn’t use the customer survey data on slide 14. Why?” Have a reason for data you intentionally excluded.
- Extension questions: “If the client decides to proceed, what would the first 90 days look like?” Think one step beyond your recommendation.
The strongest candidates treat Q&A as a conversation, not a defense. If an interviewer raises a valid point you missed, acknowledge it: “That’s a strong point — factoring in the regulatory timeline would extend the payback period by roughly 12 months.”
Common Mistakes That Sink Written Cases
Based on our experience coaching candidates through LEK’s process, these five errors account for the majority of written case failures:
mindmap
root((Written Case<br/>Failure Modes))
Time Management
Reading data packet first<br/>instead of outline slides
Spending too long<br/>on one calculation
No time to rehearse<br/>presentation
Analysis Quality
Using all 30 slides<br/>instead of filtering
Precise math on<br/>irrelevant data points
Missing the core<br/>business question
Presentation
Building suspense<br/>instead of leading<br/>with recommendation
Reading slides<br/>verbatim
Defensive posture<br/>during Q&A
1. Reading the data packet before the outline slides. This wastes 10–15 minutes reading data you may never need. Always start with the outline.
2. Attempting to use all the data. LEK deliberately includes irrelevant slides to test your ability to filter. Using everything suggests you cannot distinguish signal from noise.
3. Over-investing in one calculation. If a single calculation is consuming more than 5 minutes, estimate and move on. A complete-but-rough presentation beats a precise-but-incomplete one every time.
4. Burying the recommendation. When you open with “Let me walk you through my analysis…” instead of “I recommend the client enter the market through a $200M acquisition,” you signal that you are not comfortable with executive communication.
5. Treating Q&A as adversarial. Interviewers who challenge your numbers are testing your composure and intellectual honesty, not trying to prove you wrong.
How to Practice the Written Case
LEK’s written case format is rare enough that generic case prep does not adequately prepare you. Here is a structured practice approach:
Week 1–2: Build Component Skills
| Day | Practice Activity | Duration |
|---|---|---|
| Mon/Wed/Fri | Analyze one earnings report or investor presentation — extract 5 key insights in 15 minutes | 20 min |
| Tue/Thu | Practice chart-reading speed: given a chart, state the “so what” in under 30 seconds | 15 min |
| Daily | Mental math drills — percentages, growth rates, market sizing estimates | 10 min |
Week 3–4: Simulate Full Written Cases
Create your own written cases by downloading investor presentations from companies in LEK’s core industries (healthcare, private equity portfolio companies):
- Print 25–30 slides from the presentation
- Create 7 blank outline slides with headers matching the presentation’s themes
- Set a 60-minute timer and complete the exercise
- Present your findings to a friend or record yourself
Practice presenting to a timer — most candidates run over 20 minutes in their first few attempts. Aim to finish in 18 minutes to leave buffer for nerves on interview day.
For traditional case interview practice alongside written case prep, work through M&A cases and market sizing cases that reflect LEK’s case mix. Explore healthcare industry cases and private equity cases for industry-specific context.
LEK Written Case vs. Other Firm Formats
Understanding how LEK’s written case compares to other firms helps you calibrate your preparation.
| Firm | Written Case Format | Key Difference from LEK |
|---|---|---|
| LEK | 30-slide data packet → complete 7 outline slides → 20-min presentation + Q&A | Outline slides provided — you complete them, not build from scratch |
| BCG | Some offices use written cases with open-ended prompts | No outline structure — you design your own presentation |
| Bain | Rarely uses written cases; focuses on interactive cases | N/A |
| McKinsey | No written case; uses the McKinsey Solve assessment for screening | Entirely different format — game-based, not presentation-based |
| Deloitte | Group case presentations in some practices | Team-based, not individual |
LEK’s format is arguably the most structured: the outline slides reduce ambiguity about what’s expected but increase pressure to deliver exactly what they want.
For a broader view of how LEK’s full interview process compares to other firms, see our LEK Consulting case interview guide. You can also compare formats across firms with our BCG case interview guide and McKinsey case interview guide.
Key Takeaways
- The LEK written case is the highest-weight element in the final round — roughly 70% of rejections trace to weak written case performance rather than traditional case skills
- Always read the outline slides first, then map data packet slides to each outline slide before analyzing anything
- Allocate your 60 minutes deliberately: 5 min framing, 5 min mapping, 30 min analysis, 12 min narrative, 5 min rehearsal, 3 min math check
- Lead with your recommendation in the presentation — answer-first communication is non-negotiable at LEK
- Practice with real investor presentations from healthcare and PE portfolio companies to simulate LEK’s data-heavy format
- Treat Q&A as a collaborative discussion, not a defense — acknowledge valid challenges and show how your recommendation adapts
Ready to practice? Explore LEK cases in our case library for interactive case practice, and use the AI Mock Interview to rehearse both your analytical framing and presentation delivery with real-time feedback.