What are 'costs to achieve,' what magnitude is typical relative to run-rate synergies, and why does ignoring them flatter year-one deal math?

What interviewers are really testing

Synergy questions test whether you think like an advisor or like a spreadsheet. The math is easy; the judgment is the product.

Credibility hierarchy. The core signal interviewers listen for: cost synergies are more credible than revenue synergies, and you should say why without prompting: cost cuts are management decisions, revenue synergies require customer behavior, arrive at incremental margin rather than 100%, and are offset by attrition and dis-synergies. Candidates who treat a dollar of revenue synergy as equal to a dollar of cost synergy fail this question quietly.

The premium-vs-synergies inequality. Elite boutiques advise boards, so they want candidates who instinctively frame every synergy number against the premium: 'the deal creates value for the buyer only if the premium is less than the PV of synergies.' Being able to compute synergies paid away (premium divided by capitalized synergies) turns a definition question into an advisory answer.

Mechanics under pressure. You should be able to: tax-affect a synergy number, phase it in over 2–3 years, net off costs to achieve (rule of thumb: 1–1.5x run-rate), capitalize a run-rate into a value (divide the after-tax number by a discount rate or apply a multiple), and drop synergies into an accretion/dilution build, including solving for breakeven synergies.

The skeptic's checklist. Strong candidates volunteer how synergy estimates go wrong: double-counting savings already in the standalone plan, crediting pricing synergies that are really antitrust problems, ignoring dis-synergies, and assuming day-one run-rate with no integration spend.

A superday-caliber answer sounds like: 'I'd credit identified cost synergies at close to full value, haircut revenue synergies at least 50% and tax-affect and phase everything, then compare the resulting PV to the premium, because that comparison, not EPS accretion, is what tells the board whether they're creating or transferring value.'

Common traps

Trap 1: Treating revenue synergies like cost synergies dollar-for-dollar. A dollar of cost synergy is a dollar of pre-tax profit; a dollar of revenue synergy earns only the incremental margin on that revenue, and it depends on customers actually behaving as modeled.

Say it out loud: "A $100M cost synergy is $100M of EBIT, but a $100M revenue synergy at a 35% incremental margin is only $35M of EBIT, and it's far less certain, so I'd haircut it further before crediting it."

Trap 2: Forgetting to tax-affect synergies in EPS math. Synergies are pre-tax operating improvements; the net income benefit is synergies x (1 - t).

Say it out loud: "With $80M of pre-tax synergies and a 25% tax rate, pro forma net income picks up $60M, not $80M."

Trap 3: Assuming full run-rate from day one and ignoring costs to achieve. Synergies phase in over two to three years, and getting them costs real cash (severance, systems, facility exits), typically 1–1.5x the run-rate.

Say it out loud: "I'd phase the synergies in (say a third, two-thirds, then full run-rate by year three) and net out costs to achieve of roughly 1 to 1.5 times the run-rate in the first couple of years, so year one is usually a net cash cost."

Trap 4: Saying a deal 'makes sense because there are synergies' without comparing them to the premium. Synergies justify a premium only if their PV exceeds it; otherwise the buyer created value and handed all of it to the seller.

Say it out loud: "The test isn't whether synergies exist: it's whether the PV of synergies exceeds the premium. If we pay a $1.2B premium for $1B of synergy value, the deal destroys value for our shareholders even though the combination itself creates value."

Trap 5: Double-counting standalone improvements as deal synergies. Cost programs already in either company's standalone plan are not synergies: crediting them twice inflates the deal case.

Say it out loud: "I'd scrub the synergy plan against both standalone budgets: anything management was already going to do without the deal isn't a synergy, it's baseline."

Trap 6: Pitching pricing power as a synergy. 'We'll raise prices once we own our biggest competitor' is an antitrust admission, not a bankable synergy. Regulators read merger models.

Say it out loud: "I'd keep pricing gains out of the synergy case: anything that depends on reduced competition invites regulatory challenge, so the bankable case rests on cost overlap and genuine cross-sell."