15 Common Mistakes When Studying Investment Banking (And How to Fix Them) | LearnByTeaching.ai
Investment banking preparation demands deep fluency in financial modeling, valuation, and accounting — combined with the ability to communicate complex ideas clearly under pressure. Most candidates fail not because they lack intelligence but because they study surface-level answers without building the conceptual understanding that interviewers probe for.
Memorizing technical answers without understanding the underlying accounting
Students memorize phrases like 'depreciation is a non-cash charge' without understanding why it flows through the three financial statements the way it does. Interviewers ask follow-up questions that expose shallow memorization instantly.
A candidate says '$10 of depreciation reduces net income by $10(1-t)' but freezes when asked 'what happens to the balance sheet?' because they memorized the income statement impact without tracing the full flow: assets decrease by $10, accumulated depreciation increases, and retained earnings decrease by the after-tax amount.
How to fix it
For every 'what happens when' question, trace the full impact through all three statements: (1) Income Statement impact on EBIT and net income, (2) Cash Flow Statement adjustments, (3) Balance Sheet changes. The balance sheet must balance after every transaction. Practice until you can trace any change through all three statements fluently.
Not building a three-statement model from scratch
Students read about financial modeling in guides but never build a complete model themselves. There's no substitute for the understanding that comes from linking the income statement, balance sheet, and cash flow statement cell by cell.
A candidate claims to know financial modeling but can't explain how the cash flow statement's ending cash links to the balance sheet, or how changes in working capital are calculated from balance sheet line items, because they've never actually built the circular reference structure.
How to fix it
Build a complete three-statement model for a real public company using their 10-K filing. Start with the income statement, build the balance sheet with supporting schedules (depreciation, working capital, debt), then create the cash flow statement. Do this at least once from scratch without a template. The process takes 10-15 hours but is irreplaceable.
Treating DCF valuation as a formula instead of a framework
Students can recite 'discount free cash flows at WACC and add terminal value' but can't make the judgment calls that matter: revenue growth assumptions, margin trends, working capital needs, terminal growth rate selection, and WACC component estimation.
A candidate walks through the DCF formula perfectly but when asked 'how would you determine the terminal growth rate?' says 'I'd use 2-3%' without explaining that this should be at or below long-term GDP growth, that higher rates imply the company grows larger than the economy, and that the terminal value often drives 60-80% of the total valuation, making this assumption critical.
How to fix it
For each DCF input, understand the judgment behind it: why is this growth rate reasonable? What drives margins in this industry? Why this discount rate? Practice building DCFs for companies in different industries and notice how assumptions change. The mechanical formula is easy — the judgment is what interviewers test.
Ignoring comparable company and precedent transaction analysis
Students over-focus on DCF and under-prepare for comps and precedents, which are used more frequently in practice because they're market-based and easier to defend to clients.
A candidate can walk through a DCF but stumbles when asked how to select comparable companies, what multiples to use, and why EV/EBITDA is preferred over P/E for most analyses — revealing they've neglected the valuation methods actually used most often in IB pitchbooks.
How to fix it
Study comps analysis thoroughly: how to select comparable companies (industry, size, growth, margins), which multiples to use (EV/EBITDA for capital-structure-neutral comparison, P/E when capital structures are similar), how to apply the median multiple to the target. For precedent transactions, understand the control premium and why transaction multiples are typically higher than trading multiples.
Not understanding Enterprise Value vs. Equity Value
The distinction between Enterprise Value (value of the entire firm to all capital providers) and Equity Value (value to shareholders only) is fundamental, but students frequently confuse which metrics pair with which value.
A candidate uses P/EBITDA (equity value divided by EBITDA) instead of EV/EBITDA, mixing an equity value metric (price) with a pre-debt metric (EBITDA). This is a fundamental error because EBITDA is available to both debt and equity holders, so it must be paired with Enterprise Value.
How to fix it
Learn the matching principle: metrics available to all capital providers (EBITDA, EBIT, Revenue, Unlevered FCF) pair with Enterprise Value. Metrics available only to equity holders (Net Income, EPS, Levered FCF) pair with Equity Value. The bridge: EV = Equity Value + Net Debt + Minority Interest + Preferred Stock. Test yourself on this until it's automatic.
Weak 'Tell me about yourself' story
The behavioral component of IB interviews is often underestimated. A poorly structured 'tell me about yourself' response wastes the most important two minutes of the interview and fails to establish your narrative.
A candidate rambles through their resume chronologically, mentioning every internship and extracurricular without a clear narrative arc, leaving the interviewer unsure why this person wants to be in investment banking specifically.
How to fix it
Structure your story as a 90-second narrative with three parts: (1) Brief background that naturally leads to your interest in finance, (2) Key experiences that developed your skills (one or two max), (3) Why IB specifically and why this bank. The story should feel like a logical progression, not a resume recitation. Practice until you can deliver it naturally.
Not understanding how LBO models work
Leveraged buyout models are central to IB technical interviews, especially for candidates targeting private equity exits. Students who skip LBO modeling miss questions about returns, debt paydown, and deal structure.
A candidate is asked 'How does a PE firm generate returns in an LBO?' and can only say 'they buy cheap and sell expensive,' missing the three return drivers: (1) EBITDA growth, (2) multiple expansion, and (3) debt paydown, and how leverage amplifies equity returns.
How to fix it
Build a simple LBO model: purchase a company with 60% debt/40% equity, project cash flows for 5 years, use free cash flow to pay down debt, and calculate the equity value at exit. Understand that returns come from three sources: operational improvement (EBITDA growth), multiple expansion (selling at a higher multiple), and debt paydown (company's cash flow reduces the debt that PE didn't pay with their own money).
Not knowing industry-specific knowledge for your target group
IB is divided into industry groups (TMT, healthcare, energy, FIG, etc.) and product groups (M&A, leveraged finance, ECM, DCM). Not knowing the basics of your target group's industry signals a lack of genuine interest.
A candidate interviewing for a healthcare IB group can't name a recent major healthcare M&A deal, discuss pharma industry dynamics, or explain why healthcare companies are valued differently than technology companies.
How to fix it
For your target group, know: (1) 3-5 recent major deals, (2) key industry trends and drivers, (3) relevant valuation metrics (e.g., EV/EBITDA for most sectors, P/NAV for real estate, EV/reserves for energy), (4) major players and their competitive positions. Follow industry news through Wall Street Journal, Bloomberg, and sector-specific publications.
Confusing when to use EBITDA vs. EBIT vs. Net Income
Each profitability metric serves a different purpose. Students use them interchangeably or pick the wrong one for the analysis at hand.
A candidate suggests using EV/EBITDA to compare a capital-light software company with a capital-heavy manufacturing company, not recognizing that EBITDA ignores depreciation, which is a real economic cost for the manufacturer. EV/EBIT would be more appropriate for cross-industry comparison.
How to fix it
Understand when each metric is appropriate: EBITDA is useful for comparing companies with different depreciation policies or capital structures within the same capital-intensity level. EBIT accounts for depreciation and is better when capital intensity varies. Net Income is after interest and taxes, reflecting returns to equity holders only. Know why you're choosing each metric.
Not practicing mental math for quick calculations
IB interviews and on-the-job work require fast back-of-the-envelope calculations. Students who rely on calculators for simple math look unprepared.
A candidate is asked 'If a company has $500M revenue growing at 8% annually, what's the revenue in 3 years?' and reaches for a calculator instead of quickly estimating: $500M x 1.08^3 is approximately $500M x 1.26 = $630M.
How to fix it
Practice mental math daily: multiply and divide large numbers, calculate percentages quickly, and estimate compound growth using the Rule of 72 (72/growth rate = doubling time). For interviews, round numbers to make arithmetic easier and state your approximations clearly. Speed and confidence with numbers signals competence.
Not understanding accretion/dilution analysis for M&A
When two companies merge, the acquiring company's EPS either increases (accretive) or decreases (dilutive). Students often can't walk through the logic of why.
A candidate is asked 'Is this deal accretive or dilutive?' and guesses without understanding the framework: if the acquirer's P/E is higher than the target's P/E, an all-stock deal is accretive because the acquirer is using 'expensive' stock to buy 'cheaper' earnings.
How to fix it
Learn the quick test: in an all-stock deal, if the acquirer's P/E > target's P/E, the deal is accretive to the acquirer's EPS. In an all-cash deal, if the after-tax cost of debt used to finance the acquisition is less than the target's earnings yield (E/P), it's accretive. Practice with numbers until this logic is intuitive.
Studying alone instead of practicing with others
IB interview prep requires verbal fluency under pressure. Students who only study from guides never develop the ability to articulate technical concepts clearly and handle curveball follow-ups.
A candidate knows all the technical answers on paper but freezes in a live interview when the interviewer asks 'Walk me through how you'd value this company' because they've never practiced talking through their thought process out loud under time pressure.
How to fix it
Practice mock interviews with peers, mentors, or interview prep services weekly. Have your partner ask follow-up questions and challenge your assumptions. Record yourself and listen back — verbal stumbles, filler words, and unclear explanations that you don't notice in real-time become obvious on playback.
Not reading merger proxies and deal documentation
Students study IB from prep guides without reading real deal documents. Merger proxies, earnings transcripts, and pitch books teach you how IB actually works, not how textbooks describe it.
A candidate can define 'fairness opinion' but has never read one in a real merger proxy, so they can't discuss the actual valuation ranges used, what assumptions drove them, or how the board used the opinion in its decision-making process.
How to fix it
Read 2-3 real merger proxies (available on SEC EDGAR) and study the fairness opinions inside them. Look at the DCF assumptions, comparable company selections, and precedent transactions used. This gives you real-world examples to reference in interviews and builds practical understanding that guides alone can't provide.
Neglecting soft skills and professionalism
Technical skills get you through the screen, but fit and professionalism determine whether you get the offer. Students who only prep technicals underestimate the weight of behavioral assessment.
A candidate aces every technical question but doesn't receive an offer because they seemed arrogant in the interview, didn't ask thoughtful questions about the bank's deal flow, and couldn't articulate why they specifically wanted this bank over competitors.
How to fix it
Prepare thoughtful answers for: Why investment banking? Why this bank? Why this group? What's your biggest weakness? Tell me about a time you worked in a team/handled conflict. Research the bank's recent deals and ask specific questions. Be confident but not arrogant — IB teams work 80+ hours together and want people they'd enjoy spending time with.
Starting interview prep too late
IB recruiting timelines have moved earlier, with many banks interviewing sophomores for junior-year internships. Students who start technical prep in their junior year are often too late.
A student begins studying valuation methods in September of their junior year, only to discover that superday interviews for summer internships are already happening in October, leaving insufficient time to build genuine fluency.
How to fix it
Start technical prep at least 3-4 months before recruiting begins. Build your three-statement model and DCF over the summer. Join your university's finance club for structured preparation. Keep a timeline of target bank application deadlines and work backward from there. Early preparation compounds — starting even one month earlier makes a significant difference.
Quick Self-Check
- Can you trace a $10 increase in depreciation through all three financial statements and ensure the balance sheet balances?
- Can you explain the difference between Enterprise Value and Equity Value and which multiples pair with which?
- Can you walk through a DCF from revenue projection to share price, explaining the judgment behind each major assumption?
- Can you deliver your 'Tell me about yourself' story in 90 seconds with a clear narrative arc explaining why IB?
- Can you explain the three sources of returns in an LBO without looking at notes?
Pro Tips
- ✓Build a three-statement model for a public company using their 10-K before you start studying from prep guides; the modeling experience gives you intuitive understanding that makes memorizing technical answers unnecessary because you actually understand the mechanics.
- ✓Read 2-3 real merger proxies on SEC EDGAR and study the fairness opinions section — seeing real valuation ranges, assumptions, and comparable company selections gives you examples and credibility that textbook knowledge cannot provide.
- ✓For the 'walk me through a DCF' question, practice delivering the answer in exactly 60 seconds with a structured framework (project FCFs, calculate WACC, compute terminal value, discount to present, bridge to equity value per share) until it's second nature.
- ✓Use the Wall Street Oasis forums and Mergers & Inquisitions for interview questions, but always build deeper understanding than the one-paragraph answers provided — interviewers specifically ask follow-ups designed to test whether you actually understand the concept.
- ✓Track 5-10 recent deals in your target industry group so you can discuss them intelligently; knowing that 'Company X acquired Company Y for $Z billion at an EV/EBITDA multiple of N, which was above the sector average because...' demonstrates genuine interest and industry knowledge.