Walk me through EBITDA mechanically from net income, then explain why 'Adjusted EBITDA' exists and why it's a non-GAAP number with no fixed rulebook.

1. I start with net income and add back interest, taxes, depreciation, and amortization. That gives me reported EBITDA, but the number that actually drives a deal is Adjusted EBITDA.
2. To get to Adjusted EBITDA, management adds back items they argue are non-recurring, non-cash, or not representative of ongoing operations, like restructuring charges, stock-based comp, or transaction costs. The logic is that a buyer purchasing future cash flows shouldn't be penalized for expenses that won't repeat.
3. Adjusted EBITDA exists precisely because EBITDA itself is a non-GAAP measure. There is no GAAP rulebook that defines which adjustments are allowed or how they must be calculated, so sellers are free to construct their own version. That construction always tilts upward to make the business look more profitable.
4. Because there is no fixed standard, every add-back is contested. Buy-side diligence pressure-tests each one, and in a credit agreement, Adjusted EBITDA becomes a defined term with pages of permitted add-backs and specific caps. So the mechanical walk goes from net income to reported EBITDA, then through a judgment layer of adjustments to a number that is always a negotiated construction, not a fact.

What the interviewer is actually testing

Signal one: do you treat EBITDA as constructed, not given? The weak candidate recites the formula. The strong candidate immediately frames EBITDA as a negotiated, adjustable number and knows that "Adjusted EBITDA" is where the real work (and the real games) happen. Volunteering the distinction between reported and adjusted EBITDA, unprompted, marks you instantly.

Signal two: can you judge an add-back? Interviewers will hand you a specific add-back and watch your reaction. "The seller adds back $8M of restructuring: do you accept it?" There is no reflexive yes. The strong answer interrogates it: Has it appeared before? Is it genuinely finished, or ongoing? Is it a normal cost of running this kind of business? The differentiator is the instinct to push back, because that instinct is the job on the buy-side.

Signal three: stock-based comp. This is the single most reliable EBITDA follow-up. A strong candidate can argue both sides: it's non-cash (pro add-back), but it's a real, recurring economic cost of compensating employees that dilutes shareholders (anti add-back), and the sophisticated view is that it should generally NOT be added back: Buffett's line, "if compensation isn't an expense, what is it?" Being able to hold both sides and land on the diligence-team view signals maturity.

Signal four: the price connection. The elite candidate always closes the loop to enterprise value: an EBITDA adjustment isn't an accounting footnote, it's the adjustment times the multiple in purchase price, and it also moves debt capacity. Saying "so a disallowed $5M add-back at 10x is a $50M price cut" turns an accounting question into a deal-judgment answer, which is the register a diligence-heavy boutique wants.

How to signal mastery: when asked to define EBITDA, define it, then immediately pivot to "but the number that actually gets used in a deal is Adjusted EBITDA, and the quality-of-earnings work is about pressure-testing those adjustments, because each one moves price by the multiple." You've now answered the next three questions before they're asked.

Common traps

Trap 1: Reciting the formula and stopping. Answering "EBITDA is earnings before interest, taxes, D&A" and going silent treats a diligence question like a definitions quiz. It signals you've never seen how EBITDA is actually fought over.

Say it out loud: "Mechanically it's EBIT plus D&A, but the number that matters in a deal is Adjusted EBITDA, and the real work is in the add-backs: which are genuinely non-recurring or non-cash, and which are the seller manufacturing profit."

Trap 2: Accepting every add-back at face value. Treating the seller's "Adjusted EBITDA" as the true number is exactly the mistake QofE exists to prevent. The buy-side instinct is skepticism.

Say it out loud: "I'd interrogate each add-back: has this 'one-time' charge shown up in prior years? Are these synergies contracted or just hoped for? Would a buyer actually avoid this cost going forward? Anything that fails those tests comes back out."

Trap 3: Reflexively adding back stock-based comp. Calling SBC "non-cash, so add it back" without hesitation misses that it's a real, recurring compensation cost that dilutes shareholders.

Say it out loud: "SBC is non-cash, so it hits reported EBITDA add-back lists, but it's a genuine recurring cost of paying employees and it dilutes owners, so the diligence view is generally to leave it as an expense. If a company only looks profitable after adding back comp, that's a flag, not an adjustment."

Trap 4: Treating EBITDA as cash flow. Saying a business "generates $100M of cash" because EBITDA is $100M ignores capex, working capital, cash taxes, and cash interest.

Say it out loud: "EBITDA isn't cash flow: it's before capex, working capital, cash taxes and cash interest. A capital-intensive business with $100M EBITDA and $80M of maintenance capex converts far less to cash than a software business at the same EBITDA."

Trap 5: Missing that "one-time" charges can be recurring. Accepting a restructuring add-back without checking whether it appears every year.

Say it out loud: "If restructuring shows up three years running, it's not a one-time item: it's a recurring cost of this business, and I'd leave it in EBITDA no matter what the seller labels it."

Trap 6: Forgetting the multiple. Discussing add-backs as if they're small accounting nuances rather than purchase-price levers.

Say it out loud: "Every dollar of EBITDA is worth the multiple in enterprise value: so disallowing a $5M synergy add-back at 10x isn't a rounding item, it's a $50M cut to the price and it also shrinks how much debt the deal can carry."