"Co-executed with a Big 4 accounting firm" appears in almost every M&A engagement summary, but rarely does anyone spell out what it actually means. From either side of the table, involving a Big 4 is a question of what you get in exchange for the cost and time. This piece is the practical answer.
1. What Big 4 firms are — and are not — built for
Big 4 firms bring three assets to a deal: a methodological standard for financial due diligence, cross-border tax structuring, and a brand signal that buyers and investment committees trust. Especially in cross-border deals with U.S. PE or Japanese SI as the counterparty, a Big 4 report functions as "these numbers do not need to be re-verified."
Where Big 4 firms are structurally limited: originating deals, reading and steering the seller's negotiating psychology, and communicating in a rhythm that keeps decisions moving. Independence obligations push their tone conservative, and their staff-manager-partner pyramid rotates fast.
2. Dividing roles between Big 4 and a boutique advisor
At kickoff we put three roles on paper.
- Deal lead (boutique advisor) — sell-side / buy-side narrative, target list, negotiation cadence, ownership of the whole cycle to close.
- Financial partner (Big 4) — Quality of Earnings, normalized EBITDA, tax and legal entity structuring, financial framework for post-merger integration.
- Legal partner — SPA drafting, reps & warranties, conditions to close.
Where these three overlap, the deal slows. Where they contradict, the seller postpones the decision. Fail to nominate the lead in week one, and by the time you approach closing, no one is leading.
3. Three points that most often go wrong
First, information alignment at kickoff. If the seller's financial data set doesn't match the Big 4's request spec, the first two weeks vanish. We build a Pre-Request List with the seller's CFO within five business days and hand it to the Big 4 team. That single step saves three weeks over the whole schedule.
Second, the scope of EBITDA normalization. Big 4 methodology skews conservative. Adjustments the seller believes are legitimate — owner compensation, related-party transactions, one-time marketing spend, system rebuild costs — disappear without qualitative documentation. The boutique advisor must submit that documentation in parallel, or it doesn't make it into the QoE report.
Third, control of the VDR. Deals where the Big 4 owns the data room run at a different tempo than deals where the boutique advisor does. Whoever prioritizes and tones the answers to buyer Q&A controls the rhythm. Our default is: the boutique advisor owns the VDR and Q&A tracker, but forwards Big 4's financial/tax responses verbatim.
4. What the seller actually gains
Executing with a Big 4 is, in the end, about lowering the buyer's psychological barrier to entry. The seller absorbs 0.3–0.7% of deal size in due diligence cost, but that cost meaningfully constrains the buyer's ability to negotiate a valuation discount at the eleventh hour. A seller armed with accurate numbers does not flinch under late-stage re-negotiation pressure.
"Due diligence is not for the buyer. It is the armor that keeps you from flinching."
We tell every seller the same thing. Big 4 firms are the most trusted armorers. Where to march in that armor — that decision belongs to the seller and to the boutique advisor.