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What is a fairness opinion and why do boards commission one in M&A?

By the FES team · Published 4 January 2026

When a company's board votes to sell the business or approve a major transaction, they face an immediate problem: their fiduciary duty to shareholders requires them to determine whether the price is financially reasonable. But boards are not financial analysts. The fairness opinion is the mechanism they use — and understanding what it does and does not guarantee is essential for anyone working in or around M&A.

In brief: A fairness opinion is a formal letter from an investment bank or financial adviser to a board of directors stating that the consideration in a proposed transaction is "fair from a financial point of view" to the company's shareholders. It is a legal document, a liability shield, and the culmination of a rigorous valuation process — but it is not a guarantee that the deal is good, optimal, or that a higher price was unachievable.

Why boards commission fairness opinions

The legal and governance rationale is clear: a board that approves a sale for inadequate consideration can be sued for breach of fiduciary duty. A fairness opinion provides documented evidence that the board engaged a qualified third party, heard a professional valuation analysis, and made an informed decision. It shifts the standard of review from "did the board get the right price?" to "did the board follow a reasonable process?"

In the United States, the landmark Delaware case Smith v. Van Gorkom (1985) — in which board members were held personally liable for approving a sale without adequate financial analysis — accelerated the standardisation of fairness opinions in public M&A. Today they are obtained in virtually every material public company transaction in the US and UK.

>90% Proportion of US and UK public company M&A transactions above a material size that include at least one fairness opinion, according to academic research on deal documentation from 2000–2024.

The process: what goes into a fairness opinion

Engagement Board selects adviser Due Diligence Financials, mgmt meetings, data room Valuation DCF, trading comps, precedent transactions Board Presentation Football field chart, implied valuation range Opinion Letter "Fair from a financial point of view" Typically completed over 4–8 weeks; delivered at board meeting approving the transaction

The adviser conducts a full valuation using multiple methodologies: a discounted cash flow analysis (based on management projections), a public trading comparables analysis (how similar listed companies are valued by the market), a precedent transactions analysis (what acquirers paid in comparable historical deals), and sometimes an LBO analysis (what a financial sponsor could afford to pay and still generate acceptable returns). Each methodology produces a valuation range, and all are presented together as a "football field" chart to the board — a horizontal bar chart showing each methodology's range and where the deal price sits relative to them.

The exact wording matters

The phrase "fair from a financial point of view" is intentional and carefully scoped. It means the consideration falls within a range the adviser considers financially defensible — not that the price is the highest achievable, not that the process was optimal, and not that shareholders will be better off after the transaction than before.

A deal at £8 per share can receive a positive fairness opinion even if management privately believes £10 per share might have been achievable with more time or a different process. The opinion evaluates the price against what the business is worth, not against what might theoretically have been extracted in different circumstances.

A fairness opinion does not tell shareholders whether to vote for the deal, whether the process was well-run, or whether another bidder would have paid more. It tells the board that the consideration is financially within the realm of reasonable — and that is a narrower statement than most participants realise.

The conflict of interest problem

The adviser rendering the fairness opinion is typically paid a fee contingent on deal completion — meaning they receive full compensation only if the transaction closes. This creates an obvious structural incentive to render a positive opinion. Academic research has consistently found that negative fairness opinions — opinions concluding the price is not fair — are extraordinarily rare, occurring in fewer than 2% of deals where an opinion was rendered.

To partially address this, many boards now engage a separate independent financial adviser with a flat (non-contingent) fee to provide a second opinion, particularly for related-party transactions where the conflict of interest is most acute. This practice is now required in certain circumstances under the UK City Code on Takeovers and Mergers.

Go-shop provisions: In some private equity buyouts, the merger agreement includes a "go-shop" clause allowing the target to actively solicit competing bids for 20–60 days after signing. This post-signing market check supplements the pre-signing process, strengthens the board's fiduciary position, and is sometimes cited in the fairness opinion itself as evidence that the market has validated the price. The adviser typically delivers a "bring-down" opinion at closing to confirm continued fairness under current conditions.
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