When a buyer invokes the MAC clause, they are formally asserting that a material adverse change has occurred that relieves them of the obligation to close the acquisition. This is almost always the beginning of a negotiation, not the end of a deal — Delaware courts have upheld MAC invocations in only a handful of cases, and buyers know this, which means a MAC notice is frequently a pressure tactic rather than a genuine exit.
In my experience, the first call I get from a seller after receiving a MAC notice carries enormous emotional weight — the deal they spent years building, negotiated hard for, and announced to their team and investors appears to be unraveling. The legal reality is usually more favorable to the seller than it feels in that moment. A MAC notice is a formal legal assertion, but asserting a MAC and proving one are vastly different things. Delaware courts, which interpret the overwhelming majority of MAC clauses in acquisition agreements, have set an extraordinarily high bar for what qualifies as a material adverse change. The leading case — IBP, Inc. v. Tyson Foods — established that a MAC requires a "long-term" and "durational" impact on the company's business, not a short-term disruption. A single bad quarter, a lawsuit, a temporary loss of a customer, a broader market downturn: none of these typically qualify unless the acquisition agreement was drafted with unusual specificity. When I receive a MAC notice on behalf of a seller client, my immediate question is not "is this deal dead" — it is "what is the buyer actually trying to get."
MAC claims are rarely valid under Delaware law as courts have construed the doctrine. A qualifying MAC requires showing a substantial, durational deterioration in the target company's business — not a short-term disruption or industry-wide downturn. Broad MAC carve-outs for general economic conditions, industry trends, market disruptions, and regulatory changes frequently eliminate the buyer's argument before it begins.
I typically advise sellers to run through a two-part analysis as soon as a MAC notice arrives. First: what does the MAC definition in your purchase agreement actually say, and what are the carve-outs? Most well-negotiated acquisition agreements contain carve-outs that exclude general economic conditions, industry-wide changes, capital market volatility, regulatory or legislative changes, geopolitical events, and pandemics or acts of God. If the buyer's claimed MAC falls within one of these carve-outs, the claim likely fails on its face without reaching the merits. Second: even if the claimed event isn't carved out, does it meet the IBP standard? In IBP, the Delaware Chancery Court rejected Tyson's MAC claim despite genuine business deterioration, holding that a temporary downturn affecting a cyclical business did not qualify. In Akorn v. Fresenius — the rare Delaware case where a MAC was upheld — the deterioration was severe, widespread across multiple metrics, and the court found it was likely to be long-lasting. The evidentiary burden to actually prove a MAC is one of the highest in commercial litigation. That doesn't mean a buyer can't prevail, but it means they know the odds before they send the notice.
In the first 48 hours, the seller should retain or activate M&A litigation counsel, preserve all communications (do not delete anything), issue a formal written rejection of the MAC claim if the agreement has a cure-and-response mechanism, and avoid any public statements about the deal status. The agreement almost certainly has a termination fee or reverse termination fee provision that becomes relevant immediately.
The 48-hour window after a MAC notice is critical for several reasons, and I've seen sellers make costly mistakes in this period by acting emotionally rather than strategically. Here is what should happen in sequence. First, get your M&A counsel on a call immediately — not general corporate counsel, but someone who has litigated or seriously negotiated MAC disputes. The legal and strategic terrain is specialized. Second, read the dispute resolution and termination provisions of your purchase agreement carefully. Many agreements require the buyer to provide notice and a cure period before invoking termination rights, and missing a procedural step can be outcome-determinative. Third, issue a written response rejecting the MAC claim — this is important both to preserve your rights and to signal to the buyer that you intend to enforce the agreement. Fourth, assess your reverse termination fee. If the buyer walks away without a valid MAC, they typically owe a reverse termination fee — often 3–6% of transaction value. Understanding the economics of that alternative shapes the entire negotiation. Fifth, do not make public statements. Public statements about deal uncertainty can damage employee morale, customer relationships, and investor confidence in ways that actually support the buyer's narrative.
When a buyer invokes MAC primarily as a repricing mechanism, the seller's leverage comes from the reverse termination fee the buyer would owe if the MAC claim fails, the cost and time of litigation, and the buyer's reputational interest in closing the deals it announces. Sellers who understand the buyer's walk-away economics can often extract a deal that preserves most of the original price while giving the buyer a face-saving concession.
In my experience, the majority of MAC notices I've encountered on behalf of sellers were not genuine exit attempts — they were the opening move in a repricing negotiation. The buyer signed the deal at a particular valuation, conditions changed (market, industry, or company-specific), and they want a lower price without admitting that's what they want. The MAC clause gives them a legal frame for the conversation. Once I've understood that this is what's actually happening, the negotiation becomes straightforward in structure, if not in execution. The seller's leverage in this conversation comes from three sources. First, the reverse termination fee: if the buyer walks away and their MAC claim is invalid, they owe that fee. In a significant transaction, that can be tens or hundreds of millions of dollars, and the buyer's board has approved a deal at the original price. Second, litigation risk: MAC litigation is expensive, slow, and public. Buyers who pursue it expose themselves to discovery, deposition, and a trial in Delaware Chancery Court — none of which their board wants. Third, reputational cost: strategic acquirers and private equity buyers depend on their reputation for closing announced deals to maintain relationships with bankers, target companies, and the broader M&A community. Walking away from a deal they announced damages that reputation regardless of whether they win the legal argument. A seller who understands all three of these leverage points can often negotiate to close at something close to the original price, or extract a meaningful price adjustment in exchange for dropping the MAC dispute.
Litigation makes sense when the transaction value is large enough to justify the cost, when the buyer's MAC claim is legally weak, when the reverse termination fee is inadequate relative to the original deal value, and when the seller has strong documentation showing the alleged change does not meet the legal standard for a MAC. Specific performance — forcing the buyer to close — is sometimes available and is the most powerful remedy.
I advise sellers to think carefully about the litigation question along three dimensions. First, economics: MAC litigation is expensive and takes 12–36 months. The deal needs to be large enough that the delta between the reverse termination fee and the full deal value justifies that investment. In large transactions — $500 million and above — the math often favors litigation or the credible threat of it. In smaller transactions, the reverse termination fee may be the better recovery. Second, legal merits: how strong is the buyer's MAC claim? If the alleged change is clearly covered by a carve-out, or if it doesn't come close to the IBP durational standard, the seller's litigation position is strong. If the alleged change is genuinely severe and company-specific, be realistic about the risk. Third, remedy: what do you actually want? If you want the deal to close, specific performance may be available — many modern acquisition agreements include a specific performance right that allows the seller to compel closing rather than just collecting damages. This is the most powerful tool in the seller's arsenal, and I've seen buyers withdraw a MAC claim entirely once a specific performance motion was filed. If you primarily want money, the reverse termination fee plus damages may be the cleaner path.
MAC protection in the acquisition agreement comes from narrow MAC definitions, broad carve-outs, and strong buyer obligations. The most important protections are explicit carve-outs for industry conditions, macroeconomic events, and market volatility; a reverse termination fee sized to create real deterrence; a specific performance right; and closing conditions that minimize the gap between signing and closing.
Having been through a MAC dispute — or even just a MAC threat — most sellers want to never face this situation again. In my practice, I negotiate the MAC provisions in acquisition agreements with that goal explicitly in mind, and there are five levers that matter most. First, narrow the MAC definition as tightly as possible. The MAC should be company-specific and substantial, not a general market deterioration. Second, negotiate broad carve-outs: general economic conditions, capital markets, interest rates, exchange rates, geopolitical conditions, industry-wide trends, regulatory changes, COVID-like events, acts of God, changes in accounting standards. The more events that are carved out, the narrower the buyer's potential MAC argument. Third, size the reverse termination fee to create real deterrence. A 2% reverse termination fee on a $500 million deal is $10 million — not a meaningful deterrent to a well-capitalized buyer. 5–8% is more meaningful. Fourth, include a specific performance right that allows you to compel closing, not just collect damages. Fifth, negotiate for the shortest possible signing-to-closing timeline. Every day between signing and closing is a day on which a MAC can potentially be claimed. Regulatory approvals, HSR filings, and third-party consents that lengthen the gap increase MAC exposure, and minimizing that gap through careful structuring is one of the most undervalued protections in deal negotiation.
In my experience, the most valuable thing a seller can do when a MAC clause is invoked is to avoid panic and understand the economics before making any move. A MAC notice that arrives when the buyer is having cold feet about a deal they overpaid for is a very different situation from a MAC notice that arrives because your company genuinely suffered a catastrophic and durable decline. Most notices fall into the first category. The buyer signed a deal, conditions changed, and they want out at a lower price. Your job is to make clear — early, in writing, and with legal authority behind it — that you intend to enforce the agreement, and then to have a very honest internal conversation about what outcome you actually want: the deal at the original price, the deal at a modestly lower price, or the reverse termination fee plus freedom to find another buyer.
Gurpreet S. Bal is a Partner at Foley and Lardner LLP in Silicon Valley, where he advises startups, founders, and investors on SAFE financings, venture capital rounds, mergers and acquisitions, acquihires, and IPOs. He has represented clients in hundreds of transactions with aggregate deal value exceeding $60 billion across AI, semiconductors, fintech, and emerging technology. Prior to his career as a corporate lawyer and transaction advisor, he served with the U.S. Department of Justice and as an international and cross-border tax advisor at a Big 4 accounting firm.