Merger Arbitrage in 2026: Deal Spreads, Implied Odds, and What Happens When Deals Break

When a company agrees to be acquired for $50 a share in cash, its stock rarely trades at $50 the next day. It trades a little below, at $48 or $49, because the deal might fail, because closing is months away, and because whoever holds the shares until then wants to be paid for waiting. Merger arbitrage is the business of buying that gap, called the spread, and collecting it at closing.

The payoff is lopsided. A closed deal pays the spread; a broken deal sends the target back toward its pre-deal price, which can cost eight or more times what a successful deal earns. The largest academic study of the strategy, by Mark Mitchell and Todd Pulvino, covered 4,750 deals from 1963 to 1998 and found excess returns of about 4% a year after transaction costs. It also found that returns were uncorrelated with the stock market in flat and rising markets but fell with it in sharp declines, a pattern the authors compared to selling uncovered index put options.

This guide covers how to price a spread and read the odds it implies, how stock deals are hedged, what sets the timeline in 2026, what broken deals look like, and the costs and taxes that decide whether the strategy is worth it for an individual.

Pricing a cash deal

An illustration: a company agrees to be bought for $50 a share in cash. The stock trades at $48.50, and closing is expected in six months. Before the deal was announced, the stock traded in the mid-30s, and you estimate it would fall to about $36 if the deal broke.

The simple implied probability ignores the return on cash. If six-month Treasury bills or SOFR pay about 3.9% a year, $48.50 left in cash grows to about $49.44 in six months, and the probability that makes the deal as good as cash is ($49.44 - $36) / ($50 - $36), about 96%. That is the bar. If you think the deal has a 95% chance of closing, the expected value is $49.30, a 1.65% return over six months, less than the 1.94% on cash, and you would be taking the risk for nothing. At 98% the expected return is 2.52%.

Two assumptions drive the answer, and both deserve more work than the spread itself:

• The fallback price. The pre-announcement price is a starting point, adjusted for how the market and the company's peers have moved since. A target whose business weakened during a long review may fall below its old price.
• The timeline. If closing slips from six months to twelve, the same $1.50 spread earns 3.09% for the year, below cash. A second request or a lawsuit can do that.

Dividends the target pays before closing add to the return; many merger agreements limit them to the regular amount.

Stock-for-stock deals and hedging

In a stock deal, target shareholders receive a fixed number of acquirer shares. The target's price moves with the acquirer's, so an arbitrageur buys the target and sells short the acquirer in proportion to the exchange ratio. An illustration: each target share converts into 0.40 acquirer shares, the acquirer trades at $100, and the target at $38.80, a spread of $1.20 or 3.09%.

The hedge locks in the spread regardless of where the acquirer's stock goes, as long as the deal closes. It has costs and gaps of its own:

• The short seller pays a borrowing fee and any dividends the acquirer pays during the deal.
• Collars change the math. If the exchange ratio adjusts when the acquirer's price moves outside a range, the hedge ratio has to change too.
• Elections and proration: in deals that let holders choose cash or stock subject to limits, you may receive a different mix than you chose.
• Contingent value rights, which pay out only if a milestone is reached, need their own valuation.
• If the deal breaks, both legs can lose at once: the target falls, and the acquirer, freed from the deal, often rises.

What sets the timeline in 2026

• Shareholder votes. Mergers that need a target shareholder vote have to file and mail a proxy statement first, which usually takes a few months.
• Tender offers. A cash tender offer must stay open at least 20 business days under SEC Rule 14e-1, so uncontested tender offers can close faster than mergers that require a vote.
• HSR review. Reportable deals wait 30 days after filing (15 for cash tender offers), and most clear then. In fiscal year 2025, the agencies issued second requests, their in-depth investigations, in 41 of 1,944 adjusted transactions, or 2.1%, down from 3.0% the year before, according to the HSR annual report. Our due diligence guide covers the 2026 filing thresholds.
• In-depth investigations. Dechert's DAMITT tracker found that significant U.S. merger investigations averaged 9.9 months in the first half of 2026, more than two months shorter than in 2025, and advised parties to plan on about 10 months, or 16 to 22 months if they want time to litigate an adverse decision. The agencies reached seven merger settlements in the first half of 2026 and filed no new challenges, but state attorneys general have sued to block deals that federal agencies cleared.
• Other approvals. Foreign competition authorities, CFIUS for foreign buyers of sensitive U.S. businesses, and industry regulators such as bank, insurance, telecom, and energy agencies each add their own clock.

Read the merger agreement's outside date (the date after which either side can walk away), any extension rights, and the reverse termination fee the buyer owes if regulators block the deal. A deal with an outside date that falls before a likely court ruling is weaker than its spread suggests.

What broken deals look like

Tapestry agreed in August 2023 to buy Capri Holdings, owner of Michael Kors and Jimmy Choo, for $57 a share in cash. The FTC sued to block it, and on October 24, 2024, a federal judge granted a preliminary injunction. Capri's shares fell about 50% in the immediate aftermath, and the companies ended the deal three weeks later. There was no break fee, though Tapestry had agreed to reimburse Capri's expenses if regulators blocked the deal.

Nippon Steel agreed in December 2023 to buy U.S. Steel for $55 a share. The steelworkers' union and Donald Trump opposed the deal, and President Biden blocked it on January 3, 2025. Five months later the Trump administration approved a revised arrangement that gave the U.S. government a "golden share," and the deal was finalized on June 18, 2025 at the original $55 price, 18 months after signing. An investor who held through the block collected the full $55.

The two cases point the same way: the probability of closing can swing on a single ruling or political decision, and the timeline can stretch well past the original estimate. Deals also fail for other reasons: financing that falls through, a target shareholder vote that fails, or a buyer claiming a material adverse effect. Occasionally the surprise is favorable, when a rival makes a higher bid.

Sizing positions

• Size by the loss if the deal breaks, not by the spread. In the example, a failed deal costs about 26% of the position.
• Spread positions across many deals and across different regulators and industries. Several deals waiting on the same agency policy or the same court can fail together.
• Expect correlation in market sell-offs. Deals with financing conditions, buyers whose own stock is falling, or targets whose earnings are slipping all become riskier at the same time, which is the pattern Mitchell and Pulvino found.
• Be careful with borrowed money. Hedge funds often use it to turn thin spreads into higher returns, which also multiplies losses from breaks.

Costs, taxes, and access for individuals

Direct investing requires only a brokerage account for cash deals, plus margin and the ability to borrow shares for stock deals. It also requires reading merger agreements and regulatory filings, since the spread is only as good as the estimate of the fallback price and the timeline.

Funds do that work but charge for it, and fees take a large share of a thin spread. The AltShares Merger Arbitrage ETF's September 2026 prospectus shows a 0.75% management fee and total annual expenses of 0.82% including short-sale costs; the NYLI Merger Arbitrage ETF also charges a 0.75% management fee. Against a portfolio of spreads annualizing at, say, 5% to 7% before breaks, that is a meaningful cut. Our guides to hedge fund strategies and alternative investments cover how event-driven funds fit in a portfolio.

Most positions last less than a year, so gains are generally short-term capital gains taxed at ordinary income rates, and the completion of a cash deal is a taxable sale. Holding merger arbitrage in an IRA or other tax-advantaged account avoids that drag; our guide to tax-efficient investing covers which assets belong where.

Questions before buying a target

1. What would the stock trade at if the deal broke today, given how peers have moved since the announcement?
2. What probability does the spread imply after accounting for the return on cash, and why is your estimate higher?
3. Which approvals are still needed, from whom, and what is the realistic timeline if one of them opens an in-depth review?
4. When is the outside date, can it be extended, and is there a reverse termination fee?
5. Is the buyer's financing committed, and does the buyer still want the deal?
6. For stock deals, can you borrow the acquirer's shares, at what cost, and is there a collar?
7. How much of your portfolio would one break cost, and are other positions exposed to the same regulator or ruling?

This guide is for informational purposes only and does not constitute investment, tax, or legal advice. Merger arbitrage can lose a large part of a position when a deal fails, and short selling and borrowing add risk. The deal examples in the tables are illustrations with simplified assumptions; market data and fund expenses are as of September 2026 and change over time. Consult a qualified financial or tax adviser before investing.