M&A valuation traps CFOs keep falling into, and how to avoid them

A mid-sized industrial manufacturer completes a bolt-on acquisition at 11x EBITDAEBITDAEBITDA (Earnings Before Interest, Taxes, Depreciation, and Amortization) measures a company's operating profitability before financing and accounting decisions, used to compare core performance across firms.View full definition →. The synergy case is well-documented, the integration plan exists, and the board approved it unanimously. Two years later, the acquired business is tracking 30% below projected EBITDA, goodwill impairment is on the agenda, and the CFO who championed the deal is explaining the variance to a skeptical audit committee. This is not an unusual story. McKinsey research published over multiple years consistently shows that between 50% and 70% of acquisitions fail to create the shareholder value that justified the transaction at the time of signing. The pattern repeats because the errors are structural, not incidental.

Where valuations go wrong before a deal closes

The most common failure point is not the DCFDCFDiscounted Cash Flow (DCF) is a valuation method that estimates an asset's value by projecting future cash flows and discounting them to present value using a required rate of return.View full definition → model itself. The model is usually technically correct. The failure lives in the assumptions that feed it, and specifically in three categories that tend to be systematically optimistic.

First, revenue synergies are chronically overstated. Cross-sell projections assume customer behavior that never materializes at the expected rate. When Salesforce acquired Slack in 2021 for $27.7 billion, the integration rationale was compelling on paper, but Slack's standalone revenue growth decelerated significantly post-acquisition. Salesforce has since restructured how Slack sits within its product architecture, a signal that the commercial synergy model required revision. This is not a failure unique to Salesforce. It is a category problem. Revenue synergies require cultural alignment, product compatibility, and customer willingness to change behavior, all variables that resist precise modeling.

Second, deal teams routinely apply cost of capital assumptions that reflect conditions at the moment of origination rather than conditions across the intended holding period. In an environment like 2026, where rates have moved substantially from the 2020-2021 trough, deals that were underwritten at 6% WACC five years ago now sit in portfolios where the exit multiple compression alone has destroyed the IRRIRRThe Internal Rate of Return is the discount rate that makes a project's net present value equal zero. It expresses an investment's expected annualized return.View full definition → logic. The financing assumptions embedded in the original model were not wrong at the time; they are simply no longer the world the business operates in.

Third, integration costs are almost always underbudgeted. IT system consolidation, workforce restructuring, customer retention spend during periods of ownership uncertainty, and management distraction all carry real cost. EY and other advisory firms that publish post-deal research (and it is worth noting these firms have a commercial interest in advisory mandates) consistently flag integration cost overruns as a leading cause of value shortfalls. The data directionally aligns with independent academic work, even if the precise figures benefit from scrutiny.

What this means for the CFO

The CFO's role in M&A has expanded well beyond signing off on the financial model. Boards expect CFOs to serve as the internal skeptic, the person most likely to surface the assumption that everyone else has decided to believe because the deal has momentum.

Practically, this means building what some practitioners call a "bear case discipline" into the diligence process. Not just a downside scenario that shaves 10% off revenue projections, but a genuine stress test that asks what the business looks like if the primary synergy thesis does not materialize at all. If the deal still clears the hurdle rate in that scenario, it is probably a defensible acquisition. If it requires the synergy case to pay out on schedule to justify the price, the valuation has a structural dependency that should make the CFO uncomfortable.

For public companies, purchase price allocation is another area where CFOs often underinvest attention. The way acquired intangibles are recognized post-close, and the amortization drag that follows, directly affects reported earnings and, in some sectors, analyst perception of performance. Getting this right at close is substantially easier than correcting it afterward.

Earn-out structures deserve particular scrutiny. They are often presented as risk mitigation tools because they defer part of the purchase price contingent on performance. In practice, earn-outs frequently generate post-close disputes, particularly when the acquired management team remains in place and has different views on how the earn-out metrics should be calculated. The American Bar Association's M&A deal points studies, which track litigation and dispute patterns across thousands of transactions, show earn-out disputes as a persistent source of post-close conflict. CFOs who accept earn-out structures without pressure-testing the measurement mechanics and the governance around them inherit a problem they did not need to take on.

Working capitalWorking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition → targets at close are similarly underappreciated. A seller has every incentive to optimize working capital in the weeks before signing. Deals that do not include robust normalized working capital definitions and tight adjustment mechanisms can effectively transfer value to the seller through inventory build-up, accelerated collections, or delayed payables that unwind immediately post-close.

Practical steps worth taking before the next deal

• Run a formal post-mortem on the last two or three acquisitions your organization completed. Compare the original synergy assumptions against actual performance at 12 and 24 months. Most organizations skip this step, which means they carry the same modeling biases into the next deal.
• Separate the financial model owner from the deal sponsor inside the diligence process. When the person building the model is also the person accountable for getting the deal done, the model will find a way to support the thesis.
• Build integration cost estimates before finalizing valuation, not after. The sequence matters. Teams that price the deal and then work out integration costs discover, predictably, that the integration budget is whatever is left over after the price has been agreed.
• On earn-outs, require a draft of the earn-out calculation methodology to be reviewed by finance before term sheets are finalized, not by outside counsel reviewing a completed agreement.
• Apply a holding-period sensitivity to cost of capital. Model the IRR at the current WACC, not the WACC at origination.

The deals that destroy value in year two were usually priced incorrectly in year one. The assumptions were visible at the time; they just were not challenged with sufficient rigor. A CFO who builds a reputation for asking the uncomfortable question early, before the board has committed emotionally to a transaction, creates more durable value than one who optimizes the model to support the deal.