The Disciplines of M&A

Deal Law: the United States and the United Kingdom

Two common-law systems that answer the central question — board or shareholders — in opposite directions, and the case law each has built on that answer.

Deal Law: the United States and the United Kingdom

Public company M&A in the United States and the United Kingdom runs on two legal architectures that share a common-law ancestor and little else in practice. The US system is fiduciary-duty-driven and litigated after the fact in a specialist court; the UK system is rule-driven and regulated in real time by a panel with no US counterpart. A dealmaker who assumes a poison pill, a financing-out, or a target break fee travels across the Atlantic unchanged will misprice a transaction. This page sets out the current state of both frameworks and where they diverge in ways that matter at the negotiating table.

United States (Delaware-centric)

Why Delaware. Delaware has been the dominant domicile for large US corporations for a century, historically home to roughly two-thirds of Fortune 500 companies and, until recently, 80-93% of US initial public offerings. Its appeal rests on a deep and predictable body of corporate case law, a specialist judiciary in the Court of Chancery that hears corporate disputes without a jury, and an efficient legislature that amends the Delaware General Corporation Law (DGCL) each year to keep pace with market practice. That dominance is now under real pressure. Elon Musk's public break with Delaware after Chancellor McCormick voided his Tesla pay package led Tesla to reincorporate in Texas in 2024, and a wave of companies followed: Roblox, Affirm, Dropbox-adjacent technology names, AMC Networks, Tempus AI, Pershing Square, Fidelity National Financial and Andreessen Horowitz's fund vehicles reincorporated to Nevada, while Coinbase completed a move to Texas in December 2025 with roughly 78% stockholder approval. Between January 2024 and March 2026, approximately 49 Delaware-incorporated public companies put re-domestication proposals to a shareholder vote, 26 of them in 2025 alone, and Delaware's share of 2025 IPOs fell to around 62%, with Nevada capturing roughly 17% and Texas roughly 4% — a genuine erosion of what had been a near-monopoly (Foley & Lardner, 2026; Glass Lewis, 2025). In response, Delaware's legislature enacted Senate Bill 21 (SB 21) in March 2025, rewriting DGCL Section 144 to give boards and controlling stockholders clearer, more predictable safe harbors, and narrowing the Section 220 books-and-records inspection right that had fueled a wave of litigation-driven discovery demands. Delaware's Supreme Court unanimously upheld SB 21's constitutionality — including its retroactive application to pre-enactment transactions — in Rutledge v. Clearway Energy Group (Del. 2026), removing the near-term legal cloud over the statute. The practical read as of mid-2026: SB 21 clarified the law but has not reversed the reincorporation trend, which is now spreading beyond founder-controlled technology companies (Exxon Mobil and Dell Technologies have both been reported to be evaluating a move). "DExit" remains a live debate, and this page is a snapshot of a fast-moving position.

Structures. A US public-company acquisition is typically effected as either a one-step statutory merger, requiring a target stockholder vote and an SEC-reviewed proxy statement, or a two-step tender offer under DGCL Section 251(h), in which the acquirer makes a tender or exchange offer directly to stockholders and then completes a back-end merger without a separate stockholder vote once it holds the percentage of stock that would otherwise be needed to approve the merger. Before Section 251(h) was added to the DGCL in 2013, an acquirer that fell short of the 90% ownership needed for a short-form merger under Section 253 had to negotiate a contractual "top-up option" to cross that threshold, or fall back to a full proxy-vote merger. Section 251(h) eliminated the need for top-up options in most negotiated deals and let acquirers move from signing to closing in as little as four to six weeks via the tender-offer route, versus two to four months for a proxy vote — which is why the tender offer has become the default structure for negotiated, all-cash US public deals with financing already lined up.

Fiduciary duties and standards of review. The default standard is the business judgment rule: courts presume that directors acted on an informed basis, in good faith, and in the honest belief that their decision served the company, and will not second-guess a decision made under that presumption absent a showing of disloyalty, bad faith, or gross negligence. Several doctrines displace that presumption in specific settings. Revlon (Revlon v. MacAndrews & Forbes, 1986) holds that once a company is in "Revlon mode" — a sale or change of control has become effectively inevitable — the board's task shifts to securing the best value reasonably available to stockholders, tested by enhanced judicial scrutiny of the process rather than a single mandated procedure. Unocal (Unocal Corp. v. Mesa Petroleum, 1985) governs a board's defensive response to a hostile bid: the board must show reasonable grounds, based on a good-faith and reasonable investigation, that a threat to corporate policy existed, and that its response was proportionate to that threat — not preclusive or coercive. Corwin (Corwin v. KKR Financial Holdings, 2015) holds that an informed, uncoerced vote of disinterested stockholders approving a merger invokes business judgment review of the whole transaction, effectively cleansing process flaws that might otherwise draw enhanced scrutiny — except where a controlling stockholder stands to receive a non-ratable benefit, in which case Corwin cleansing does not apply. That carve-out is where MFW (Kahn v. M&F Worldwide, 2014) operates: a controller-led going-private merger earns business judgment review, rather than the more demanding entire fairness standard, only if the controller conditions the deal from the outset on approval by both an independent, empowered special committee and an uncoerced, informed vote of a majority of the disinterested minority stockholders. SB 21 has meaningfully altered this landscape. As rewritten, DGCL Section 144 lets a board cleanse most controlling-stockholder conflict transactions with either a proper special committee or a majority-of-the-minority vote — not necessarily both — while going-private transactions specifically still require both protections, essentially codifying MFW's conjunctive test for that narrower category and relaxing it for controller transactions that fall short of a full going-private. This is a real loosening of pre-SB 21 Delaware common law for the broader set of controller conflicts, and it is the amendment most contested by the plaintiffs' bar and institutional investors.

Appraisal rights. DGCL Section 262 lets a stockholder who did not vote for a qualifying merger demand a judicial determination of the "fair value" of its shares in the Court of Chancery, in lieu of the merger consideration. For years this fueled "appraisal arbitrage," in which funds bought shares after a deal was announced solely to pursue a Chancery valuation that sometimes exceeded the deal price. Delaware's Supreme Court curtailed that trade through a pair of decisions holding that a merger price produced by an open, arm's-length, competitive process is entitled to significant — potentially dispositive — weight as evidence of fair value: DFC Global Corp. v. Muirfield Value Partners (Del. 2017), which applied that principle to a financial-sponsor buyout, and In re Appraisal of Dell Inc. (Del. 2017), which extended it to a management buyout with a more limited pre-signing market check, rejecting the notion that a financial sponsor's involvement alone should disqualify reliance on deal price. Verition Partners Master Fund v. Aruba Networks (Del. 2019) pushed further, holding Chancery had erred in giving no weight to the target's unaffected 30-trading-day average market price. Together with 2016 statutory amendments allowing an acquirer to prepay estimated fair value to stop interest from accruing, and a de minimis carve-out excluding very small stakes from appraisal in non-vote transactions, this line of authority sharply reduced the expected return to appraisal arbitrage, and dedicated appraisal funds have largely retreated from the trade.

Defences. The poison pill (shareholder rights plan) remains lawful in Delaware — Moran v. Household International (1985) upheld its basic validity — but its deployment is reviewed under Unocal's proportionality test, and Delaware courts have struck down "dead hand" and "no-hand" pill features that would prevent a newly elected board from redeeming the plan (Quickturn Design Systems v. Shapiro, 1998; Carmody v. Toll Brothers, 1998). Modern pills are typically adopted defensively in response to rapid activist accumulation or market dislocation, set at a low trigger threshold (often 10-15%), and run for a limited term of about a year, frequently with shareholder ratification built in. Paired with a classified (staggered) board — directors split into classes serving staggered multi-year terms, so a hostile bidder cannot replace a board majority in a single annual meeting even with clear majority stockholder support — a pill gives a Delaware board genuine "just say no" power: Air Products v. Airgas (Del. Ch. 2011) is the leading illustration, where a staggered board and pill together let the Airgas board reject a fully financed, all-cash tender offer for well over a year. What a board cannot do is use defensive measures that are preclusive or coercive, or maintain them for entrenchment rather than a good-faith belief that the offer undervalues the company, and once a company is in Revlon mode a board's obligation shifts from resisting a sale to obtaining the best price reasonably available.

Disclosure and process. A merger requiring a target stockholder vote proceeds by proxy statement under Exchange Act Section 14(a); where the acquirer is issuing registered stock as consideration, that proxy is combined with a Form S-4 registration statement into a joint proxy statement/prospectus, reviewed by the SEC. A tender offer instead proceeds under the Williams Act (Exchange Act Sections 14(d) and 14(e)) and Regulation M-A, with the bidder filing a Schedule TO and the target responding with a Schedule 14D-9 recommendation statement; the Code's minimum 20-business-day open period for a tender offer is the rough US analogue to the UK's fixed statutory timetable, though far less prescriptive.

United Kingdom

The Takeover Code and the Panel. UK public takeovers are governed by the City Code on Takeovers and Mergers, administered by the Panel on Takeovers and Mergers, which sits on a statutory footing under Part 28 of the Companies Act 2006. The Panel regulates in real time — issuing rulings, granting dispensations, and enforcing a fixed timetable as a deal unfolds — rather than adjudicating after the fact through litigation, which is the Delaware model. The Code's guiding philosophy is shareholder primacy and procedural fairness: target shareholders, not the target board, should decide the outcome of an offer, and all shareholders should be treated equally and kept informed. Three rules capture most of what a US practitioner needs to unlearn.

Rule 21 — board neutrality and frustrating action. Once a target board has reason to believe a bona fide offer is imminent, or has received one, it cannot — without shareholder approval — take any action that could frustrate the offer, including issuing shares, disposing of material assets, or entering contracts outside the ordinary course of business. In substance, a UK board cannot unilaterally deploy a poison pill or any comparable defensive device; frustrating action of that kind requires the shareholders' own consent. This is the single largest structural difference between the two systems. Where a Delaware board can resist a hostile bid for an extended period using a pill and a staggered board, a UK board's defensive toolkit is limited to persuasion — better terms, a competing bidder, or a public case to shareholders that the offer is inadequate — because the Code, not fiduciary litigation, sets the outer limit of board action.

Rule 9 — the mandatory offer at 30%. Any person, together with those acting in concert with it, who acquires shares carrying 30% or more of a company's voting rights — or who already holds between 30% and 50% and acquires even one further share — must make a general offer to all other shareholders in cash (or with a cash alternative) at no less than the highest price paid in the preceding 12 months. There is no US equivalent: a mandatory-offer obligation is triggered automatically by the arithmetic of the shareholding, not by a board or bidder decision, and it applies regardless of whether the acquirer intended to make a takeover bid at all. Amendments effective February 2026 refined how Rule 9 applies to dual-class share structures and to buybacks that push an existing large shareholder through the 30% line, but the core 30% trigger is unchanged.

Put up or shut up — Rule 2.6. Once a potential bidder is publicly named in connection with a possible offer, it has 28 days from that announcement either to announce a firm intention to make an offer under Rule 2.7 or to announce that it does not intend to proceed — the "PUSU" deadline. The Panel can extend the deadline at the target board's request, but a bidder that walks away, or lets the clock run out, is normally barred from approaching the target again for six months, subject to a competing-offer exception. There is no equivalent forcing mechanism in US deal practice; a potential US acquirer can often remain undisclosed, and unconstrained by a public clock, through much of a negotiation.

Scheme of arrangement vs contractual offer. Recommended UK deals are usually implemented as a scheme of arrangement, a court-supervised procedure under Part 26 of the Companies Act 2006 rather than a takeover offer in the US sense. A scheme requires approval at a shareholder meeting by a majority in number of those voting and at least 75% by value of the shares voted, followed by a court sanction hearing, after which the scheme binds 100% of shareholders on a single completion date with no residual minority — there is no separate squeeze-out step. Because a scheme needs the target board's cooperation to convene the meeting, it cannot be used for a hostile approach. A contractual offer, by contrast, is made directly to shareholders and can be pursued without target board support, but full control requires reaching 90% acceptances of the shares to which the offer relates before the acquirer can invoke the statutory squeeze-out under Part 28 of the Companies Act 2006 to compel the remaining minority to sell; falling short of 90% leaves a continuing minority and complicates delisting. Schemes dominate recommended transactions because they deliver certain, complete control in one step without depending on an acceptance threshold that determined minority holders can sometimes frustrate — the trade-off is that a scheme is only available where the target board is willing to convene it.

Certain funds. Under the Code, a cash offeror must have the necessary cash resources available before it announces a firm intention to bid, and its financial adviser must publicly confirm that those resources are in place. This "cash confirmation" requirement is what UK practitioners call the certain funds regime, and it is why UK cash offers essentially cannot carry a financing condition — the money has to already be certain when the offer is announced, not merely committed subject to conditions. US deals are not barred from including a financing condition as a matter of law, though strategic acquirers rarely use one in practice; the UK position turns the market norm into a Code requirement.

Break fees. Rule 21.2 generally prohibits the target company from agreeing to pay any inducement fee (break fee) to a bidder, which reverses the direction US practitioners expect: in the US it is routinely the target that agrees to pay the disappointed bidder a break fee — commonly in the range of 2-3.75% of deal value — if it walks away for a superior proposal. The Code allows narrow exceptions, chiefly a fee payable to a favoured bidder in a genuinely competitive situation or a formal sale process, capped at 1% of the target's value and payable only if that bidder's own offer succeeds. The default UK position is that the target simply cannot buy a bidder's goodwill with a fee at all.

The National Security and Investment Act 2021. In outline, the NSIA gives the UK government power to scrutinise, and if necessary block, unwind, or condition, acquisitions of control raising national security concerns. It imposes mandatory pre-closing notification for qualifying acquisitions crossing 25%, 50% or 75% of shares or voting rights (or gaining "material influence") in 17 specified sensitive sectors spanning defence, advanced technology, critical infrastructure and data; closing a mandatory transaction without clearance renders it void. A separate, broader call-in power lets the government examine other qualifying transactions, in any sector, within a five-year retrospective window. This page covers the regime only in outline; a dedicated wiki page addresses NSIA screening and its practical effect on deal timetables in depth.

The comparison that matters

Crossing the Atlantic, a dealmaker has to re-learn six things at once. Defence availability inverts: a US target can deploy a pill and a staggered board to buy time and force better terms, while a UK board is largely disarmed by Rule 21 and must win the argument in public rather than block the clock. Deal certainty inverts with it: a UK scheme delivers all-or-nothing control on a single completion date, while a US merger can leave a residual appraisal claim even after the vote or tender succeeds, though the Dell/DFC line has narrowed that risk. Financing conditionality is a Code-mandated impossibility in UK cash offers under the certain funds rule, where it is merely rare, not prohibited, in US practice. Break fees run in opposite directions — routine target-to-acquirer fees in the US, a general prohibition on any target fee in the UK, with only a narrow competitive-situation carve-out. Timetable rigidity is a Panel-enforced feature of every UK offer, with PUSU's 28-day clock and the Code's fixed offer calendar, against a US process that is comparatively negotiable and shaped by the parties' own merger agreement covenants rather than a regulator's calendar. And disclosure of the bidder itself differs: a named UK bidder is locked into a public, time-limited process the moment it is identified, while a US bidder can often preserve confidentiality, and optionality, well into a negotiation. None of these differences is cosmetic — each reallocates leverage between bidder, target and shareholders, and a term that is standard on one side of the Atlantic can be unavailable, or backwards, on the other.

This page is a general reference on public company deal law in the United States and United Kingdom. It is not legal advice and should not be relied on as a substitute for advice from qualified counsel in the relevant jurisdiction.

The other disciplines

• The Volume of M&A Over Time
• Merger Control and Antitrust Review
• Foreign Investment and National Security Screening
• Deal Law: Continental Europe and Asia
• Cross-Border M&A
• Accounting for M&A
• Tax in M&A
• The Deal Process and the Documents
• Valuation, Due Diligence and Integration
• Who Buys, and With What Money