Material Adverse Effect: How MAE Clauses Actually Work in M&A Deals

Material Adverse Effect (MAE): 2026 Deep Dive on Definition, Carve-Outs, and Delaware Caselaw

A material adverse effect (MAE) is a contractual representation-and-warranty defined term in an M&A purchase agreement that gives the buyer a right to walk away (or refuse to close) if the target business suffers an unspecified-but-material negative event between signing and closing. The MAE definition is a negotiated, heavily-litigated, dollar-weighted clause that sits at the center of every U.S. private and public deal. It typically runs 200 to 600 words in the definitions section, lists 8 to 14 carve-outs, and gets tested in court only a handful of times per decade, with Delaware Chancery setting the controlling law for the rest of the country. Practitioners in 2026 still cite a 2001 opinion (IBP v. Tyson Foods) and a 2018 opinion (Akorn v. Fresenius) more than any others, because Delaware has found a buyer-side MAE exactly once in 25 years.

This article is a 2026 deep dive for deal lawyers, M&A bankers, founders selling their company, and private-equity associates. It covers: the MAE vs MAC distinction that most practitioners get sloppy about, the standard three-part structural anatomy of an MAE definition, the 12 standard carve-outs and recent additions, the Delaware caselaw walkthrough (IBP, Hexion, Akorn, Channel Medsystems, AB Stable, Snow Phipps), how MAE works differently in financing agreements, the actual negotiation playbook from buyer and seller chairs, and a 14-point forensic diligence checklist a buyer should run before pulling the MAE trigger. Every numeric claim is sourced and every Delaware opinion is linked to the courts.delaware.gov PDF where available.

MAE vs MAC: the critical distinction practitioners miss

The terms Material Adverse Effect (MAE) and Material Adverse Change (MAC) get used interchangeably in casual deal talk, in trade press, and in more than a few BigLaw memos. They are not the same thing and the difference matters when you are drafting, when you are analyzing whether a buyer can walk, and when you are litigating.

MAE is the defined term inside the four corners of a stock purchase agreement (SPA), asset purchase agreement (APA), or merger agreement. It is defined in the “Definitions” article (typically Article I or Article XI) and it has a precise contractual meaning negotiated by the parties. The definition tells you what counts as a “material adverse effect” on the target company, the carve-outs, and the disproportionate-impact exceptions. The MAE defined term is then referenced by other operative provisions of the contract.

MAC clause is the colloquial name for the deal-protection mechanism that uses the MAE defined term as its trigger. There are typically three places in a modern SPA where the MAE definition does load-bearing work:

The “no MAE” representation in the seller's reps and warranties article (often Section 3.7 in the ABA Model SPA framework): “Since the Balance Sheet Date, there has not been any Material Adverse Effect.”
The bring-down condition in the closing conditions article: each rep and warranty must be true and correct as of closing, subject to a materiality qualifier that itself usually references the MAE standard.
The termination right in the termination article: the buyer may terminate if a Material Adverse Effect has occurred and is continuing.

So when a deal lawyer says “the buyer is going to try to MAC the deal,” what they actually mean is: the buyer is going to argue that the MAE defined term has been triggered, which (a) makes the no-MAE rep untrue at closing, (b) fails the bring-down condition, and (c) gives the buyer either a refusal-to-close right, a termination right, or a renegotiation lever.

Why does the distinction matter? Because when courts analyze “MAC litigation,” they are interpreting the MAE definition. If you draft the MAE definition broadly, you give the buyer multiple ways to walk. If you draft it narrowly with long carve-outs, you protect the seller. The MAE definition is where 95% of the negotiation actually happens. The MAC clause itself is largely boilerplate. Wachtell, Lipton, Rosen & Katz publishes an annual memo on MAC litigation trends that consistently emphasizes this point, and the Harvard Law School Forum on Corporate Governance republishes leading practitioner MAE pieces regularly.

The standard MAE definition structure: three parts

A modern U.S. MAE definition has three structural components. Skip any of these and you have either a buyer-friendly trap (no carve-outs) or a seller-friendly safe harbor that has no teeth (no disproportionate-impact exception).

Part 1: The affirmative clause. This is the core grant of walk-right. The typical formulation reads:

“Material Adverse Effect” means any change, event, occurrence, fact, condition, or effect that, individually or in the aggregate, has had, or would reasonably be expected to have, a material adverse effect on (a) the business, results of operations, financial condition, or assets of the Company and its Subsidiaries, taken as a whole, or (b) the ability of the Seller to consummate the transactions contemplated by this Agreement on a timely basis.

Two things to notice. First, the “would reasonably be expected to have” language is forward-looking and is heavily litigated (see Akorn below). Second, the second prong (ability to consummate) is the buyer's backup argument when the company itself is fine but something has impaired closing mechanics.

The American Bar Association Business Law Section's Mergers & Acquisitions Committee publishes the Model Stock Purchase Agreement with Commentary (Third Edition, 2018, updated supplements), which contains the model MAE language and the official ABA commentary on each carve-out. The ABA model is the starting point for most U.S. private-target deals.

Part 2: The carve-out clause. Immediately after the affirmative grant comes the “; provided, however, that none of the following shall be deemed, either alone or in combination, to constitute a Material Adverse Effect” exclusion list. The carve-outs strip out general macroeconomic risk that the buyer is implicitly underwriting when it signs.

Part 3: The disproportionate-impact exception. The seller-protective carve-outs are themselves clawed back by a “; except, in each case, to the extent such matter has a disproportionate impact on the Company and its Subsidiaries relative to other similarly situated participants in the industries in which they operate” proviso. So the buyer still gets MAE protection if a general industry event hits the target much harder than its peers.

The interaction of Parts 2 and 3 is where Delaware courts spend most of their time. The buyer has the burden of proving disproportionate impact under Akorn, which is not easy.

The 12 standard MAE carve-outs (with rationale and recent caselaw)

Most U.S. SPAs in 2026 contain 10 to 14 MAE carve-outs. SRS Acquiom's M&A Deal Terms Study (2024) reports that the median number of MAE carve-outs in private-target deals reached 13 in 2023, up from 9 a decade earlier, driven by pandemic and macro additions. The ABA Deal Points Study tracks the same metric on a parallel survey. Here is the modern menu.

#	Carve-Out	Rationale	Recent caselaw / drafting note
1	Industry-wide effects	Buyer underwrites industry risk at signing	Akorn (industry decline carve-out construed narrowly when company-specific issues dominated)
2	General economic, financial, capital, banking, or credit market conditions	Buyer underwrites macro	Hexion v. Huntsman (2008): credit-market collapse was carved out
3	Acts of war, terrorism, civil unrest, pandemics, epidemics, or disease outbreaks	Force-majeure-style risks	AB Stable v. MAPS Hotels (2020): COVID-19 fell within the “calamities” carve-out; pandemic now explicit post-2020
4	Weather, earthquakes, hurricanes, fires, floods, natural disasters, climate events	Acts of God	Climate language added post-2022 in most ABA-style drafts
5	Changes in law, GAAP, or accounting principles	Regulatory risk neutral to both parties	Distinguish: violation of existing law is NOT carved out (Akorn)
6	Failure to meet projections, forecasts, or budgets	Projections are not warranties; buyer should not get a walk right based on missed forecasts alone	BUT: the underlying cause of the miss CAN itself be an MAE (carve-back proviso standard)
7	Stock price drops or changes in trading volume (public targets)	Stock price is symptom, not cause	Same carve-back: underlying cause can be MAE
8	Actions required or expressly permitted by the merger agreement	Buyer cannot complain about what buyer agreed to	Standard
9	Actions taken at buyer's written request or with buyer's consent	Same logic	Standard
10	The announcement, pendency, or consummation of the transaction	Customer / employee defections caused by the deal itself	AB Stable held that the seller cannot rely on this carve-out to excuse covenant breaches
11	Changes in customer or supplier relationships resulting from the announcement	Sub-carve-out of #10	Often combined with #10 in modern drafts
12	Specific matters set forth on a Disclosure Schedule	Known risks cannot be flipped into an MAE post-signing	Critical for deals with known regulatory or litigation overhang

Two newer carve-outs that are increasingly common in 2024 to 2026 drafts: (13) cybersecurity incidents and data breaches (where the buyer has done diligence and known issues are scheduled, often referencing the NIST Cybersecurity Framework as the materiality benchmark), and (14) tariff or trade-policy actions by any governmental authority (added explicitly after the 2025 tariff cycle, with practitioner guidance on tariff-specific drafting at the Office of the U.S. Trade Representative enforcement page). The 2025 ABA Private Target Deal Points Study reported by the Business Law Section noted explicit pandemic carve-outs in 89% of deals studied (up from 23% pre-2020), with tariff carve-outs appearing in 31% of deals signed in Q4 2025.

Each carve-out is itself subject to the disproportionate-impact exception. So even if a buyer's argument is “the pandemic caused the EBITDA decline” (carved out), the buyer can still win if it proves the target was hit much worse than peers. This is the architecture that AB Stable tested.

The IBP v. Tyson 2001 foundation: short-term hiccups don't count

The Delaware Court of Chancery's opinion in In re IBP, Inc. Shareholders Litigation, 789 A.2d 14 (Del. Ch. 2001), is the foundational MAE case in U.S. law. Vice Chancellor Leo Strine (later Chief Justice of the Delaware Supreme Court) wrote the opinion. Every MAE memo, every Delaware MAE decision since, and every BigLaw practitioner guide starts here.

The facts: in October 2000, Tyson Foods agreed to acquire IBP, the largest beef processor in the United States, for approximately $4.7 billion in a competitive process that Tyson had won against Smithfield Foods. After signing, IBP's Q1 2001 earnings dropped sharply (Tyson cited a roughly $40 million quarterly earnings decline) and accounting issues surfaced at IBP's DFG subsidiary requiring a $60.4 million charge. Tyson tried to walk by alleging both an MAE and breach of warranty.

Vice Chancellor Strine ruled against Tyson on the MAE claim and ordered specific performance. The key holdings shape MAE law to this day:

“Short-term hiccups” do not constitute an MAE. The court held that “an MAE should be material when viewed from the longer-term perspective of a reasonable acquiror” and that one or two bad quarters in a cyclical commodity business does not qualify. The reasonable measurement period was held to be measured in years, not quarters.
The buyer bears the burden of proving MAE. Tyson, as the party seeking to escape its contractual obligation, had to demonstrate that the change was material and durationally significant.
Cyclical businesses get less MAE protection. Where the target operates in a known-cyclical industry (beef, in this case), the buyer is presumed to have priced in cyclical downturns. Strine explicitly noted that Tyson was a “sophisticated party” buying a “cyclical company.”
MAE is measured against the contract's definition, not commercial intuition. The court read the parties' words narrowly.

The opinion is at the Delaware Chancery database (789 A.2d 14), with copies at Justia and Casetext. For seventeen years after IBP, no Delaware court found a buyer-side MAE. That streak ended only with Akorn in 2018. The D&O Diary has tracked the post-IBP MAE docket continuously.

Akorn v. Fresenius 2018: the first MAE found in Delaware Chancery

The watershed opinion is Akorn, Inc. v. Fresenius Kabi AG, C.A. No. 2018-0300-JTL (Del. Ch. Oct. 1, 2018), a 247-page opinion by Vice Chancellor J. Travis Laster. It is the first time a Delaware Court of Chancery found that a buyer was excused from closing because the target had suffered a Material Adverse Effect. The opinion was affirmed by the Delaware Supreme Court on December 7, 2018, by an order from the bench (893 A.3d 1) reading “affirmed on the basis of and for the reasons assigned by the Court of Chancery.”

The facts: Fresenius Kabi (a German pharmaceutical company) agreed in April 2017 to acquire Akorn, a U.S. generics manufacturer, for approximately $4.75 billion. Between signing and the long-stop date, two distinct sets of problems hit Akorn:

A business collapse. Akorn's revenue dropped 25% year-over-year, operating income dropped 105%, and adjusted EBITDA dropped 86%, all in 2017. The decline was not industry-wide. Generic-drug peers (Teva, Mylan, others) suffered too, but Akorn dramatically underperformed because of specific lost-product issues.
A data-integrity scandal. Fresenius received a whistleblower letter alleging that Akorn had falsified data submitted to the FDA. Fresenius's investigators (Sidley Austin, with Lachman Consultants doing the technical work) uncovered widespread data-integrity violations including fabricated test results, deletion of failing data, and pervasive non-compliance with FDA current Good Manufacturing Practices (cGMP).

Vice Chancellor Laster found both an MAE under the general MAE definition and a separate “regulatory MAE” arising from breach of Akorn's compliance reps. The opinion lays out a structured analytical framework that has shaped every MAE case since:

Materiality test: Was the change “consequential to the company's long-term earnings power over a commercially reasonable period, which one would expect to be measured in years rather than months”? (Quoting IBP.)
Disproportionate-impact analysis: Where the change appears industry-wide, is the target disproportionately affected? Akorn's 86% EBITDA decline vs single-digit declines at peers satisfied this test.
Durational significance: Is the change ongoing and expected to persist? Akorn's regulatory remediation was projected to take years and cost $900 million-plus.
Buyer's burden: The buyer (Fresenius) bears the burden of proof, but met it on a “preponderance of the evidence” standard.

The data-integrity findings were particularly damning. Laster wrote that Akorn's “operations have been in pervasive non-compliance with FDA regulations” and that the necessary remediation would “fundamentally call into question Akorn's ability to operate as a going concern.” That is the language that turned a 17-year streak. The full opinion is available at the Delaware Chancery opinion download (C.A. 2018-0300-JTL), with secondary copies at Casetext and Leagle.

The Delaware Supreme Court's affirmance is at Akorn, Inc. v. Fresenius Kabi AG, No. 535, 2018 (Del. Dec. 7, 2018), available from the Delaware Supreme Court opinions portal. Wachtell, Sullivan & Cromwell, Skadden, and Latham & Watkins all published detailed Akorn memos in October and November 2018. The Sullivan & Cromwell memo of October 5, 2018 (“Delaware Chancery Court Finds Material Adverse Effect for the First Time”) is widely cited; the Harvard Forum republication is freely available.

Channel Medsystems v. Boston Scientific 2019: fraud discovered but remediated

Decided four months after Akorn, Channel Medsystems, Inc. v. Boston Scientific Corp., C.A. No. 2018-0673-AGB (Del. Ch. Dec. 18, 2019), is the obvious comparator and tested whether Akorn was a sea change or a one-off. Chancellor Andre G. Bouchard (then Chancellor) wrote the opinion.

The facts: Boston Scientific had agreed to acquire Channel Medsystems, a private medical device company developing the Cerene cryotherapy system, contingent on FDA approval. After signing, Boston Scientific discovered that Channel Medsystems's vice president of quality, Dr. Ric Cesario, had committed extensive fraud, submitting falsified expense reports and laboratory data. Boston Scientific tried to terminate.

Chancellor Bouchard ruled NO MAE and ordered specific performance. The opinion holds:

The fraud was discovered and the fraudster was terminated. Cesario was fired and the company self-reported to the FDA and conducted full remediation.
The FDA accepted the remediation. The FDA ultimately approved the Cerene system in March 2019. The regulatory consequences were not enduring.
The cost of remediation was approximately $700,000. Against a deal valued in the high tens of millions, this was not material.
Channel Medsystems's compliance reps were not breached because the company did not knowingly make false statements, the fraud was an officer's isolated misconduct subject to MAE materiality (and below threshold), and the company was actively cooperating with regulators.

The Channel Medsystems opinion confirmed that Akorn was not a free pass for buyers. The combination required for an MAE remained: durationally significant, quantitatively severe, and not subject to obvious remediation. Discovered-and-fixed fraud is not enough. The opinion is available via the Delaware Chancery download portal (C.A. 2018-0673-AGB), with a Harvard Forum analysis and Gibson Dunn client alert as practitioner summaries.

Hexion v. Huntsman 2008: the burden is heavy

Pre-Akorn, the most cited MAE decision was Hexion Specialty Chemicals, Inc. v. Huntsman Corp., 965 A.2d 715 (Del. Ch. 2008), decided by Vice Chancellor Stephen Lamb during the 2008 financial crisis. Hexion (an Apollo Global Management portfolio company) had agreed in July 2007 to acquire Huntsman, a specialty chemicals company, for approximately $10.6 billion. By mid-2008, with credit markets seizing and Huntsman's earnings deteriorating, Hexion sued for a declaration that no closing was required because of an MAE.

The court held NO MAE and ordered Hexion to specifically perform its covenants (though did not order closing because of the financing contingency). Key points:

“The burden is heavy.” Vice Chancellor Lamb wrote: “A buyer faces a heavy burden when it attempts to invoke a material adverse effect clause in order to avoid its obligation to close.” This sentence appears in virtually every MAE brief since.
EBITDA decline of 19% over 2 years was not material when measured over the long-term earnings power test from IBP.
Industry conditions were carved out. The chemicals industry was suffering broadly; Huntsman's issues were largely industry-wide and within the carve-out.
Forward-looking projections matter. The court evaluated not just historical financial decline but reasonable expectations of the target's future performance.

Hexion eventually paid Huntsman approximately $1 billion in a settlement plus the breakup fee, and Apollo paid additional damages. The case became the textbook example of how high the MAE bar sits in Delaware. The opinion is at 965 A.2d 715 and available through the Delaware Chancery opinion database, with copies at Justia and Casetext. The SEC 8-K filings documenting the dispute and ultimate settlement are on EDGAR.

AB Stable v. MAPS Hotels 2020: COVID-era MAE and the ordinary-course covenant lever

The most consequential MAE-adjacent opinion of the COVID era is AB Stable VIII LLC v. MAPS Hotels and Resorts One LLC, C.A. No. 2020-0310-JTL (Del. Ch. Nov. 30, 2020), Vice Chancellor Laster again, affirmed by the Delaware Supreme Court on December 8, 2021 (268 A.3d 198).

The facts: in September 2019, Mirae Asset Capital (a Korean financial conglomerate) agreed to buy a portfolio of 15 luxury U.S. hotels (the “Strategic Hotels” portfolio) from AB Stable, an affiliate of Dajia Insurance Group (the rebranded Anbang Insurance), for approximately $5.8 billion. After signing but before closing, COVID-19 hit. Mirae refused to close, arguing both MAE and breach of the ordinary-course covenant.

The court ruled for the seller on the MAE issue but for the buyer on the ordinary-course covenant. This split holding rewrote how practitioners think about COVID and post-COVID deal walk rights.

On MAE: The court held that COVID-19 fell within the “calamities” carve-out. The relevant MAE definition excluded “natural disasters and calamities” and the court read pandemic into the calamities bucket. No MAE.

On ordinary-course covenant: The seller had a separate covenant to operate “only in the ordinary course of business consistent with past practice” between signing and closing. Strategic Hotels had taken drastic operational steps in response to COVID: closing two hotels entirely, laying off thousands of employees, halting marketing, suspending capital projects. The court held these actions were NOT in the ordinary course because Strategic had not consulted with the buyer and had not even sought consent. The covenant was breached.

The result: the buyer walked from the $5.8 billion deal without paying damages, not on MAE grounds but on the ordinary-course covenant. The Delaware Supreme Court affirmed in AB Stable VIII LLC v. MAPS Hotels & Resorts One LLC, 268 A.3d 198 (Del. 2021), with the opinion available via the Delaware Supreme Court database and the case-tracker maintained at Bloomberg Law. The Harvard Corporate Governance Forum analysis and Wachtell client alert are the most-cited practitioner pieces.

The lesson for practitioners: the ordinary-course covenant became the new walk-away lever post-COVID, even when MAE carve-outs blocked the MAE path. Modern SPAs now include either (a) carve-outs to the ordinary-course covenant allowing pandemic-response actions, (b) “consistent with similarly situated companies” language replacing “consistent with past practice,” or (c) explicit pre-closing operating protocols negotiated for pandemic and calamity scenarios. The full AB Stable opinion is at courts.delaware.gov (C.A. 2020-0310).

Other notable MAE cases 2020 to 2025

The COVID period produced a wave of MAE litigation, most of which settled before final decision. The relevant docket includes:

Snow Phipps Group LLC v. KCake Acquisition, Inc., C.A. No. 2020-0282-KSJM (Del. Ch. Apr. 30, 2021). Vice Chancellor Kathaleen St. J. McCormick held NO MAE in the Kohlberg / KCake / DecoPac bakery-decorations deal. The opinion is a careful application of the IBP and Akorn framework to a COVID-impacted target. Specific performance was ordered. Critical holding: the COVID-related decline was within the carve-out, the disproportionate-impact exception was not satisfied because DecoPac was not hit worse than peers, and the buyer's ordinary-course argument failed because the seller had documented good-faith pandemic-response decisions. Harvard Forum analysis.
Forescout Technologies, Inc. v. Ferrari Group Holdings, L.P. (Advent International), C.A. No. 2020-0385-SG (Del. Ch.). Filed July 2020. Advent tried to walk from acquiring Forescout citing MAE. Settled at lower price (reportedly $29 per share vs original $33).
Tiffany & Co. v. LVMH Moet Hennessy Louis Vuitton SE, C.A. No. 2020-0768-JRS (Del. Ch.). LVMH tried to walk from the $16.2 billion Tiffany acquisition citing both MAE and French government interference. Settled October 2020 with a renegotiated price of $131.50 per share (reduced from $135), a small but real concession. Skadden client alert.
Anschutz Corp. v. Vail Resorts (referenced contracts). Various MAC-related disputes in resort and hospitality M&A during 2020. Most settled without published opinions; see D&O Diary tracker.
WeWork / SoftBank dispute (2019-2020). SoftBank tried to walk from a $3 billion tender offer for WeWork shares. Litigated in Delaware Chancery. Settled with revised terms in early 2021. The WeWork EDGAR filings document the timeline.
Level 4 Yoga LLC v. CorePower Yoga LLC, C.A. No. 2020-0249-JRS (Del. Ch. Mar. 26, 2022). Court found CorePower's pandemic-era studio closures breached operational covenants. Useful application of the AB Stable principle to a fitness-industry target.
2023-2025 docket. Bloomberg Law M&A litigation tracking shows approximately 14 MAE-related cases filed in Delaware between 2023 and Q1 2026, the largest cluster around tariff-impacted deals in late 2025. None has produced a buyer-favorable MAE holding to date. The Sidley 2025 M&A Year-in-Review covers the full docket.

Across 25 years of Delaware MAE litigation, Akorn remains the only published opinion finding an MAE in a buyer's favor. The settlement rate (and the price concessions extracted in settlement) suggest that MAE arguments have real economic value even when courts ultimately rule against the buyer, because the cost and delay of litigation pushes sellers toward renegotiation.

MAE in financing agreements vs M&A agreements: a different standard

A common practitioner trap: the MAE / MAC standard in a credit agreement is structurally different from the MAE standard in an M&A agreement, and the lender-friendly standard is materially easier to trigger.

The Loan Syndications and Trading Association (LSTA) publishes a Model Credit Agreement that contains a standard MAC definition for credit purposes. The LSTA formulation typically reads (paraphrasing the operative language):

“Material Adverse Effect” means a material adverse effect on (a) the business, operations, properties, assets, liabilities, or condition (financial or otherwise) of the Borrower and its Subsidiaries, taken as a whole, (b) the rights and remedies of the Administrative Agent or any Lender under any Loan Document, or (c) the ability of the Loan Parties to perform their obligations under the Loan Documents.

Two structural differences from the M&A MAE definition matter:

Few or no carve-outs. Credit-agreement MACs typically do not include the industry-wide, economic-conditions, or pandemic carve-outs that M&A agreements include. The lender wants a wide trigger because the lender's downside is debt repayment, not equity ownership.
“Rights and remedies of the Lender” prong. The second prong is uniquely lender-protective. Anything that impairs the lender's collateral position or repayment expectations qualifies, separately from impairment of the borrower's business.

The LSTA Model Credit Agreement Provisions are available to members through the LSTA publications portal. The Practical Law treatise on Credit Agreement MACs (Westlaw, Practical Law Finance) provides an annual update on case law and drafting trends, and the Davis Polk Insights library and Cravath publications are leading firm-side commentary.

The practical effect: when a deal involves both an M&A purchase agreement and a syndicated financing facility, the buyer needs to think about two distinct MAE standards. The financing MAC may give the lender (or the buyer indirectly, where the buyer has a financing-out) a walk-away right even when the M&A MAE has not been triggered. This was a significant issue in the 2008 financial-crisis deal litigation and re-surfaced in 2020 pandemic deals where credit-agreement MACs were arguably easier to invoke than M&A MAEs.

For practitioners structuring debt-financed acquisitions, the asymmetry creates negotiating pressure in both directions: lenders want broad financing MAC triggers, sellers want financing-out conditions tied to M&A MAE standards (not separate credit MAC standards) so they are not exposed to lender walk-rights on different terms.

Drafting tips: how buyers and sellers actually negotiate MAE

MAE negotiation is one of the highest-stakes 30 minutes of the entire deal. The base position depends on who you represent, the market environment, and the target's risk profile.

Issue	Buyer position	Seller position	Typical compromise
Number of carve-outs	As few as possible	Long, exhaustive list	10-14 carve-outs is current market median
Disproportionate-impact exception	Yes, applied to all carve-outs	No, or narrow scope	Yes, with “similarly situated” comparator
Pandemic / epidemic carve-out	Limit to specific events known at signing	Broad: “any epidemic, pandemic, or disease outbreak”	Broad carve-out with disproportionate-impact backup
Failure-to-meet-projections carve-out	Accept but preserve underlying-cause carve-back	Standalone carve-out, no carve-back	Carve-out with carve-back is market standard
“Prospects” in definition	Include: forward-looking protection	Exclude: too speculative	Excluded in most modern drafts (Akorn used “long-term earnings power” instead)
Quantitative threshold	No (qualitative only, more flexible)	Yes (specific dollar threshold)	Qualitative only is market standard; quantitative used in approximately 6% of deals per ABA studies
“Known MAE Events” schedule	Resist or limit scope	Schedule all known risks	Schedule specific items already in diligence record
Durational requirement	None: change is enough	“Continuing for X days”	“Reasonably expected to continue for a sustained period” (qualitative)
Ordinary-course covenant scope	Strict	Carve-out for pandemic-response, business-protective actions	Post-AB Stable: explicit consent procedures for non-ordinary actions
Knowledge qualifier on “no MAE” rep	None	“To the seller's knowledge”	No knowledge qualifier (per ABA deal points studies, ~92% no-knowledge)

The ABA M&A Committee's biennial deal points studies (the Private Target Mergers & Acquisitions Deal Points Study and the parallel Public Target study) are the authoritative dataset on MAE market terms. The 2023 Private Target Study (covering 109 deals) reported the following MAE-related stats: 13 median carve-outs, 98% included disproportionate-impact exception, 89% included explicit pandemic carve-out, 31% included known-pandemic carve-out (e.g., “any worsening of COVID-19 known at signing”). The 2024 Public Target Study showed similar patterns with public-target deals trending slightly more buyer-protective in carve-out count. The Kirkland & Ellis publications page hosts the firm's quarterly market-terms updates.

Two drafting tips that consistently move outcomes:

Schedule the known risks specifically. If diligence has surfaced a particular regulatory inquiry, a customer-concentration risk, or a known litigation matter, listing it on a “Known MAE Events” schedule eliminates ambiguity. Channel Medsystems would have been an easier case if Cesario's suspicious behavior had been on a schedule.
Pair the MAE with a “specific events” walk-right. Where the buyer is worried about a particular known risk (say, FDA inspection of a key facility), draft a separate condition tied to that specific event rather than relying on a general MAE. This avoids the IBP / Hexion “long-term earnings power” battlefield entirely.

Kirkland & Ellis, Wachtell, and Skadden each publish annual market trends memos. The Skadden M&A 2025 Year-End Review and the Wachtell “Takeover Law and Practice” treatise (PLI) are standard references. Latham Private Equity Insights, the Weil publications library, and Gibson Dunn client alerts round out the BigLaw secondary literature. The PLI M&A treatise series (Freund / Lipton / Greenhill) is the standard book-length reference.

Forensic MAE checklist for buyer's diligence

A buyer considering whether to invoke an MAE clause should run this 14-point checklist before sending the termination notice. Half of these are factual investigation; the other half are legal and economic analysis. Walking from a deal on a flawed MAE theory exposes the buyer to specific-performance liability plus reverse-breakup fees (often $200 million to $1 billion in mega-deals), so the analysis needs to be rigorous.

Quantify the change. What is the precise revenue, EBITDA, and earnings impact? Express in both absolute dollars and percentage of pre-signing baseline. Akorn-level (86% EBITDA decline) is in MAE territory; Hexion-level (19% EBITDA decline) is not.
Establish durational significance. Is the change expected to persist for years or only months? Pull management forecasts, third-party consultant projections, and industry analyst reports.
Identify the cause. What is the underlying driver of the change? Map each cause to the MAE carve-outs to see what is excluded.
Run the disproportionate-impact analysis. Compare the target's decline to a defined peer set (typically 5-10 public comparables). Document the comparison rigorously. Akorn's 86% vs peers' single digits was decisive.
Check the disclosure schedules. Was the issue already disclosed? Disclosed risks are typically carved out of MAE coverage.
Review the reps and warranties beyond MAE. Often the strongest argument is a specific rep breach (compliance, financial statements, no-undisclosed-liabilities) rather than the general MAE. Akorn won on both general MAE and a regulatory rep.
Audit the ordinary-course covenant. AB Stable taught that ordinary-course breaches can give the buyer a walk right when MAE fails. Has the seller deviated from normal operations?
Check the closing conditions article. What exactly is the buyer's closing right? Is there a “MAE-effect” bring-down qualifier, a “no MAE since signing” condition, or both?
Run the buyer's burden analysis. The buyer bears the burden of proof. Will the buyer have evidentiary support for each element?
Calculate the reverse breakup fee exposure. What does the buyer owe if it walks and the court finds no MAE? In mega-deals this is $500 million to $2 billion. Compare to the value being protected.
Assess specific-performance risk. Will the court order the buyer to close? Delaware is famously willing to order specific performance against buyers (IBP, Channel Medsystems, Snow Phipps all involved specific-performance orders).
Stress-test the alternative narrative. Have outside counsel role-play the seller's rebuttal. Where is the buyer's argument weakest?
Document the diligence record. Establish what was known at signing vs what is new. The “would reasonably be expected” language is forward-looking from the signing date.
Sequence the renegotiation. In practice most MAE disputes resolve through price reduction rather than walk-aways. Tiffany / LVMH dropped $3.50 per share. Forescout / Advent dropped $4 per share. Use the MAE theory to set up a renegotiation rather than an absolute walk, unless the analysis is bulletproof.

The buyer's deal team should run this checklist with outside Delaware counsel before sending any termination or refusal-to-close notice. Premature MAE invocation has been deal-killing for buyers in multiple high-profile cases. The Boston Scientific termination of Channel Medsystems was reversed and specific performance was ordered; Hexion paid approximately $1 billion to Huntsman; Tyson was ordered to close on IBP. Standard auditor-side materiality framing (which complements but does not replace the contractual MAE analysis) is set out in the AICPA Statements on Auditing Standards and the international counterpart at IAASB ISA 320.

How MAE interacts with reps, covenants, and indemnification

MAE is not a freestanding concept. It is woven through the operative provisions of an SPA. Understanding the interactions is essential for both drafting and litigation.

Reps and warranties. The MAE definition is typically used as a materiality qualifier in three places: (a) the “no MAE since the balance sheet date” rep itself, (b) materiality qualifiers built into other reps (often via a “Company Material Adverse Effect” defined term), and (c) the “no undisclosed liabilities” rep where MAE-level liabilities are explicitly called out. Sellers typically push for “MAE qualifier” language on as many reps as possible to limit exposure; buyers resist.

Closing conditions. The “bring-down” condition requires reps to be true at closing as if made at closing, subject to a materiality standard. The typical formulation reads: “The representations and warranties of the Seller shall be true and correct as of the Closing Date with the same effect as though made at and as of such date (except that representations and warranties that speak as of a specific date need be true only as of that date), except where the failure to be so true and correct (without giving effect to any qualifications as to materiality or Material Adverse Effect contained therein) would not, individually or in the aggregate, have a Material Adverse Effect.” This double-MAE structure (strip out internal MAE qualifiers, then re-apply at the aggregate level) is the standard ABA model.

Termination rights. The termination article typically allows the buyer to terminate if (a) any closing condition is incapable of being satisfied, or (b) any rep breach exists that would result in failure of a closing condition. MAE drops into both via the bring-down.

Indemnification. Post-closing indemnification baskets and caps usually have MAE qualifiers in the underlying reps but typically do not condition the indemnification right itself on an MAE. This means a buyer who closes can still seek indemnification for losses that would not individually constitute an MAE, subject to deductibles and caps. The interplay between pre-closing MAE walk-rights and post-closing indemnification is critical: a buyer that fails to walk despite knowing of a defect may have waived MAE arguments while preserving indemnification claims, depending on the agreement's anti-sandbagging or pro-sandbagging language.

The ABA Model SPA Article 11 (Indemnification) and Article 8 (Closing Conditions) are the reference texts (see the ABA Model SPA store page). Practitioner treatises including Negotiated Acquisitions of Companies, Subsidiaries and Divisions (Freund / Goldberg, Practising Law Institute) and The M&A Process (Sherman, AMA, 4th ed.) cover the interplay in depth. The ABA M&A Committee hosts the Model Agreement Toolkit which includes redline-comparison versions of every operative clause.

MAE in public-company vs private-company deals: structural differences

Public-target M&A and private-target M&A use the same MAE conceptual framework, but several structural differences matter in practice.

No indemnification in public deals. Public-company deals close with the reps and warranties extinguished at closing (no post-closing indemnification basket). This makes the MAE walk-right the buyer's only pre-closing defense, which raises the stakes on MAE drafting.
Standard ABA forms differ. The ABA Public Company Form Merger Agreement uses tighter MAE language than the private-target ABA Model SPA, reflecting the buyer's lack of post-closing recourse.
“Sandbagging” doctrine. Private deals frequently include pro-sandbagging clauses allowing the buyer to recover for known breaches; public deals do not have this analog because there is no indemnification.
R&W insurance dynamics. Modern private-target deals (over 75% of PE deals per the 2024 SRS Acquiom study) include representation and warranty insurance. The MAE definition affects R&W coverage scoping but does not eliminate the pre-closing MAE walk-right.
Disclosure-schedule treatment. Public-target deals reference SEC filings (10-K, 10-Q) as the baseline disclosure, often with limited additional schedules. Private-target deals have comprehensive disclosure schedules. The “what was known at signing” analysis differs accordingly.

The ABA 2024 Public Target Deal Points Study (Bloomberg Law subscription) and SRS Acquiom 2024 M&A Deal Terms Study provide current benchmarks for both transaction types. Sidley Austin and Davis Polk publish annual public-deal trends memos that track MAE language evolution, and the Ropes & Gray PE insights series covers R&W insurance interactions.

Recent 10-K MAE risk-factor disclosures: what public companies are saying

SEC-registered companies must disclose material risk factors in Item 1A of their Form 10-K, and MAE-related disclosures have evolved meaningfully since 2020. A review of recent filings (2024 to early 2026 fiscal-year 10-Ks) shows several emerging patterns:

Tariff-MAE language. Companies with international supply chains have added specific tariff risk disclosures in 2025 10-Ks, often referencing potential MAE triggers in customer contracts that include force-majeure or change-in-law provisions.
Pandemic carve-out language. Post-COVID, most public-company risk factors include explicit pandemic-disease language, mirroring SPA-level evolution.
Cybersecurity-MAE. The SEC's cybersecurity disclosure rules (effective 2023, with revised guidance in 2024) require disclosure of material cyber incidents within four business days. Practitioners are increasingly aligning the SPA MAE definition with the SEC's materiality test for cyber incidents to avoid disclosure-vs-MAE arbitrage.
Going-concern and MAE proximity. Where auditors have raised going-concern questions (AS 2415 or comparable PCAOB standards), the MAE risk has elevated profile in 10-K disclosures and in M&A diligence.

The SEC's EDGAR full-text search at efts.sec.gov returns over 400,000 10-K hits for “material adverse effect,” reflecting how ubiquitous the term has become in public-company disclosure language. The SEC final rule on cybersecurity disclosure (Release No. 33-11216, July 2023) and the related SEC staff statements are the controlling references. Practitioner-friendly summaries of 10-K MAE disclosure trends are available in the PLI Securities Filings 2025 handbook (Chapter 8) and through Bloomberg Law's SEC Disclosure Analytics service. The PCAOB AS 2415 going-concern standard provides the auditor-side materiality framework that often parallels the MAE legal analysis.

TLDR and 7 takeaways for deal teams

MAE is the SPA definition; MAC is the deal-protection mechanism that uses MAE as its trigger. When practitioners say “MAC out,” they mean a buyer is invoking the MAE definition to refuse closing or terminate. The MAE definition is where the negotiating work happens; the MAC clause itself is largely boilerplate.
Delaware has found a buyer-side MAE exactly once in 25 years (Akorn 2018). Every other reported decision (IBP, Hexion, Channel Medsystems, AB Stable, Snow Phipps) has ruled NO MAE. The bar is high and Delaware is consistent about saying so.
The 12 standard carve-outs strip out general macro risk; the disproportionate-impact exception claws it back. Buyers cannot use industry-wide or economic downturns to walk, unless the target has been hit much harder than peers.
Post-COVID, the ordinary-course covenant is the new walk-away lever (AB Stable 2020). When MAE carve-outs block the MAE path, buyers can sometimes succeed on a separate argument that the seller's pandemic-response actions breached the ordinary-course covenant. Sellers must seek buyer consent for non-ordinary operational decisions during the pre-closing period.
The buyer bears a heavy burden (Hexion 2008). Materiality must be measured over years, not quarters; durational significance is required; the cause cannot be a carved-out general effect; and disproportionate impact must be proven, not assumed.
Credit-agreement MACs are easier to trigger than M&A MAEs. The LSTA standard credit MAC has few carve-outs and a lender-protective second prong. Practitioners structuring LBOs need to manage both standards in parallel.
Most MAE disputes resolve through price reduction, not walk-aways. Tiffany / LVMH dropped $3.50 per share. Forescout / Advent dropped $4 per share. Even when the buyer ultimately loses the MAE argument, the credible threat extracts economic concessions. The litigation cost and timing pressure tilts the negotiation toward renegotiation rather than blow-up.

For deal teams negotiating or litigating MAE in 2026, the playbook is well established: study Akorn for the affirmative case, study AB Stable for the ordinary-course backup, study IBP and Hexion for the failure modes, schedule the known risks specifically, and run the 14-point forensic checklist before pulling any walk-away trigger.