State the intuitive P/E-arbitrage rule for when an all-stock deal is accretive versus dilutive to the acquirer's EPS, with no synergies assumed.

What interviewers are really testing

This is the highest-frequency quantitative M&A question at elite boutiques because it's fast to ask, hard to fake, and reveals whether a candidate understands MECHANISM versus VALUE. Interviewers want three things, escalating in difficulty:

First, the P/E-arbitrage intuition, cold and fast: 'stock deal is accretive when the acquirer's P/E is higher than the P/E it's effectively paying for the target', said instantly, without derivation, because it should be internalized.

Second, the ability to derive breakeven premium and breakeven synergies live, with real numbers. This is almost always asked as a numerical prompt: 'Acquirer trades at 20x, target at 14x, all-stock deal, no synergies, accretive or dilutive?' followed immediately by 'how much could we pay before it turns dilutive?' A strong candidate sets up the relative-P/E logic before reaching for a calculator, and can articulate what changes if the deal is instead debt- or cash-funded (breakeven premium math changes because there's no share dilution to fight against, only incremental after-tax interest cost).

Third (and this is what separates a strong candidate from an excellent one): the immediate, unprompted caveat that accretion/dilution is not a value-creation metric. Interviewers specifically listen for whether a candidate says something like 'but I'd want to check this against the cost of capital / whether returns exceed WACC' without being pushed. Candidates who treat accretion as inherently 'good' get a pointed follow-up designed to expose that gap ('so a value-destroying deal can never be accretive?').

Signal mastery by naming the specific terms that enter the EPS bridge (synergies after-tax, incremental interest after-tax, incremental D&A after-tax, new share count) rather than a vague gesture at 'combined earnings over combined shares.'

Common traps

Trap 1: Treating accretion as proof of a good deal. Accretion/dilution is a mechanical byproduct of relative P/E and financing choice: it says nothing directly about whether the deal creates value versus its cost of capital.

Say it out loud: "Accretion tells me the deal raises pro forma EPS given the financing and price paid: it doesn't tell me whether the deal creates value. I'd want to check whether the expected return on the target exceeds our cost of capital before calling it a 'good' deal."

Trap 2: Forgetting synergies are credited AFTER-TAX in the EPS bridge, but often quoted PRE-TAX by management. Mixing pre-tax and after-tax figures in the same bridge produces a wrong breakeven number.

Say it out loud: "I always tax-effect synergies before adding them to net income in the bridge: if management quotes a pre-tax synergy target, I multiply by (1 minus the tax rate) before it enters my numerator."

Trap 3: Forgetting the opportunity cost of cash in a cash-funded deal. Using balance-sheet cash to fund a deal isn't free: the acquirer forgoes the after-tax interest income that cash was earning, which should reduce pro forma net income just like new debt's interest expense would.

Say it out loud: "Even in an all-cash deal funded from the balance sheet, I still deduct the after-tax interest income we're giving up on that cash: it's not a free source of funding."

Trap 4: Computing breakeven premium using the WRONG P/E (announcement vs. deal-implied). The breakeven analysis must compare the acquirer's OWN standalone P/E to the P/E the acquirer is EFFECTIVELY PAYING for the target at the proposed price, not the target's pre-deal trading P/E.

Say it out loud: "The comparison is my P/E versus the P/E I'm paying for the target's earnings at the DEAL price, not the target's standalone trading multiple before any premium is applied."

Trap 5: Ignoring incremental D&A from purchase accounting write-ups in the EPS bridge. Write-up depreciation and new intangible amortization (lessons 45-46) are real, recurring, after-tax expenses that reduce pro forma net income: a bridge that only includes interest and synergies is incomplete.

Say it out loud: "I also need to include the after-tax incremental D&A from any PP&E write-up and new intangible amortization created by purchase accounting: that's a real recurring drag on GAAP EPS that's easy to leave out if you only think about financing costs and synergies."