Every acquisition announcement leans on the same word: synergies. The acquirer says the combined company will be worth more than the two standalone businesses added together, and that extra value is the synergy. But "synergies" is often used loosely in press releases and pitch decks, and interviewers expect candidates to be precise about what the term actually covers, and about why not all synergies are created equal.
The Two Kinds of Synergies
Synergies split into two categories, and the distinction matters far more than most candidates realize going into an interview.
Cost synergies come from eliminating duplicate spending: redundant headcount, overlapping facilities, duplicated corporate functions (finance, legal, IT), and better procurement terms from combined purchasing volume. Cost synergies are largely within management's direct control — if you decide to close a duplicate distribution center, that saving happens on a predictable timeline.
Revenue synergies come from the combined company selling more than the two businesses would have sold separately: cross-selling one company's products through the other's sales force, bundling products, or using a combined footprint to enter new markets. Revenue synergies depend on customer behavior, competitive response, and execution quality that the acquirer doesn't fully control.
Why the Distinction Matters
Experienced dealmakers, and by extension interviewers, treat these two categories very differently when they underwrite a deal. Cost synergies are typically discounted less heavily and realized on a faster, more predictable timeline. Revenue synergies are notoriously overestimated in deal models — studies of completed M&A repeatedly find that acquirers realize a much smaller share of projected revenue synergies than of projected cost synergies. A model that treats both types of synergy as equally certain is a red flag in an interview setting, because it signals the candidate hasn't internalized this well-known asymmetry.
Synergies Aren't Free — There's a Cost to Achieve
Realizing synergies isn't free. Integrating two companies' systems, severance for redundant employees, and consulting fees for the integration itself are all real, near-term cash costs — usually called the "cost to achieve." A synergy case that only shows the upside without netting out this one-time cost is incomplete, and an interviewer will typically ask about it directly if you don't bring it up yourself.
From Concept to Number: Risk-Adjusting and Discounting
Once you understand the two categories, the next skill interviewers test is turning "the deal will generate $80m of run-rate synergies" into an actual number you'd underwrite. That means phasing synergies in over time rather than assuming they appear on day one, applying a realization probability (lower for revenue synergies than for cost synergies), taxing the after-effect cash flows, and discounting them back to present value — often at a rate higher than the acquirer's normal WACC, to reflect the extra execution risk of integration.
You can walk through this full calculation, with real numbers, in Synergy Valuation, which builds a risk-adjusted, after-tax, discounted synergy value and compares it to the premium paid for the deal — the exact comparison an acquirer's board would want to see before signing off.
Where Synergies Fit in the Bigger Picture
Synergy valuation doesn't happen in isolation — it feeds into the acquirer's broader deal math. It's one input into whether a deal is accretive or dilutive to earnings, and it interacts with how the acquirer thinks about the maximum price it can justify paying, a question explored from the buy-side in How PE Thinks About Valuation. Understanding synergies clearly is also what lets you push back, in an interview, on an unrealistic deal premise — a skill that separates a strong candidate from one who just accepts the numbers on the page.