The Most Common Valuation Mistakes Interviewers Exploit

Introduction

Interviewers do not ask valuation questions to test whether you have memorized formulas. They ask them to test whether you understand valuation conceptually, practically, and intuitively. The most effective way they do this is by probing for common mistakes: errors that reveal a superficial understanding that breaks down under scrutiny. This article catalogs the most frequently exploited mistakes and explains how to avoid each one.

Every mistake in this article has been covered in the relevant technical section of this guide. This article brings them together as a checklist specifically designed for interview preparation.

The error: Suggesting EV/Net Income or Equity Value/EBITDA as a valuation multiple.

Why it is wrong: The matching principle requires that the numerator and denominator represent the same investor group. Enterprise value represents value to all capital providers; net income is available only to equity holders. Equity value represents value to equity holders; EBITDA is available to all capital providers. Mismatching produces a meaningless ratio.

The test: "What multiple would you use to compare these companies?" If you suggest EV/Net Income or Price/EBITDA, the interview is effectively over for that question.

The fix: Always think about who has a claim on the denominator. Pre-interest metrics (EBITDA, Revenue, EBIT) pair with enterprise value. Post-interest metrics (net income, EPS, book value of equity) pair with equity value.

The error: Calculating Enterprise Value = Equity Value + Debt without subtracting cash and cash equivalents.

Why it is wrong: Cash is a non-operating asset whose returns are not captured in EBITDA. An acquirer who buys a company with $2 billion in cash effectively receives that cash, reducing the net cost of acquisition. The full bridge is: EV = Equity Value + Debt + Preferred + Minority - Cash.

The test: "Walk me through the equity value to enterprise value bridge." Or the more pointed: "Why do we subtract cash?"

The fix: Cash is subtracted because it is a non-operating asset that does not contribute to the operating metrics (EBITDA, Revenue) that EV pairs with.

The error: Calculating equity value (market cap) using basic shares outstanding instead of diluted shares.

Why it is wrong: Basic shares ignore stock options, warrants, RSUs, and convertible securities that will or could create new shares. Using basic shares overstates the per-share value.

The test: "How do you calculate equity value?" If you say "share price times shares outstanding" without specifying diluted shares, the interviewer will probe.

The fix: Always specify diluted shares. Explain the treasury stock method for options and warrants, and the if-converted method for convertible securities.

The error: Stating that if a company borrows $500 million, its enterprise value increases by $500 million.

Why it is wrong: When a company borrows, debt increases by $500 million but cash also increases by $500 million (the proceeds sit on the balance sheet). In the EV bridge, the increase in debt and the increase in cash offset each other perfectly. Enterprise value does not change because the operating business has not changed.

The test: "If a company issues $500 million in new debt, what happens to equity value and enterprise value?" The correct answer: neither changes immediately (assuming the market views the transaction as value-neutral).

The error: Using EV/EBITDA to value a bank, insurance company, or other financial institution.

Why it is wrong: For banks, debt is an operating asset (deposits fund lending), not financing. Including all bank "debt" in enterprise value produces a meaninglessly large number. And interest expense is a core operating cost for banks, so EBITDA is not a relevant profitability measure.

The test: "How would you value a bank?" If you lead with EV/EBITDA, the interviewer knows you do not understand FIG valuation.

The fix: Banks are valued on P/TBV (price-to-tangible book value) and P/E, with the DDM as the intrinsic method. Explain why EV/EBITDA fails and what replaces it.

The error: Using a terminal growth rate of 4-5% (or higher) in a DCF for a US company.

Why it is wrong: The terminal growth rate represents the rate at which the company's cash flows grow forever. A rate above long-term nominal GDP growth (approximately 3-3.5% for the US) implies the company will eventually become larger than the entire economy, which is impossible.

The test: "What terminal growth rate would you use and why?" The correct range is 2-3%, approximately in line with long-term GDP growth.

The error: Including a convertible bond both as debt in the EV bridge AND as dilutive shares in the share count.

Why it is wrong: This double-counts the claim. If the convertible is in-the-money and will convert, remove it from debt (it becomes equity) and add the conversion shares. If it is out-of-the-money and will not convert, keep it as debt and do not add shares. Never both.

The test: "How do you treat convertible bonds in valuation?" The key insight: if converting, treat as equity (remove from debt, add shares). If not converting, treat as debt (keep in bridge, no shares).

The error: Stating "the company is worth $47 per share" without presenting a range or sensitivity analysis.

Why it is wrong: Every valuation methodology depends on assumptions that involve judgment. The output is inherently uncertain, and presenting a single number implies false precision that does not reflect the reality of the analysis.

The fix: Always present a range. "The comps analysis suggests $42-50 per share, the DCF suggests $44-54, and precedent transactions suggest $48-58. The convergence zone is approximately $47-52, which I would present as the defensible valuation range." This demonstrates that you understand valuation is art, not science.

The error: Being unable to answer "which valuation method typically gives the highest value and why?"

The standard ordering: Precedent transactions (highest, because they include control premiums) > DCF (depends on assumptions) > Trading comps (current market pricing without premium) > LBO (lowest, constrained by return targets and leverage).

The nuance: This ordering is not fixed. The DCF can produce the highest or lowest value depending on assumptions. In a market bubble, comps may exceed precedent transactions. In a tight credit market, the LBO floor drops significantly. Explaining these exceptions demonstrates deeper understanding than simply memorizing the standard ordering.

The error: Responding to "walk me through a DCF" by reciting the formula without explaining the logic.

Why it is wrong: The interviewer wants to hear the reasoning, not the math. Why do we project cash flows? (Because a company is worth its future cash generation.) Why do we discount? (Because of the time value of money and risk.) Why WACC? (Because we are discounting UFCF, which is available to all capital providers.) What does the output represent? (Enterprise value, which must be bridged to equity value per share.)

The fix: Lead with concepts, support with formulas. "A DCF values a company by projecting its future free cash flows and discounting them to present value, reflecting the principle that a dollar today is worth more than a dollar tomorrow." Then walk through the five steps with both the logic and the mechanics.