Merger arbitrage spreads on the largest pending US deals range from about 1.6% to about 15% as of September 4, 2026, and the size of each spread tracks the risk the market sees in closing. Norfolk Southern trades about 14.9% below the value of Union Pacific's cash-and-stock offer, which reflects a long rail regulatory review, while Warner Bros. Discovery trades 9.7% below Paramount Skydance's $31 cash price during antitrust litigation [1][3][6]. Deals with fewer obstacles, such as Sun Pharma's purchase of Organon, trade at spreads under 2% [5][6].
What is a merger arbitrage spread?
After a deal is announced, the target's shares usually trade below the offer value. The gap is the spread. An investor who buys the target (and, in a stock deal, sells short the buyer's shares in the exchange ratio) earns the spread if the deal closes, but can lose much more if it fails and the target falls back toward its pre-deal price. The spread therefore prices three things: the time until closing, the cost of money over that time, and the probability that the deal breaks.
Merger arbitrage spreads on pending mega-deals in 2026
The table uses closing prices on September 4, 2026, from DataPorium's stock data, and the deal terms in each company's or regulator's documents [1][3][4][5][6].
| Deal | Terms per target share | Target price | Offer value | Gross spread |
|---|---|---|---|---|
| Union Pacific / Norfolk Southern | 1 UNP share + $88.82 cash | $329.46 | $378.44 | 14.9% |
| Paramount Skydance / Warner Bros. Discovery | $31.00 cash | $28.25 | $31.00 | 9.7% |
| NextEra Energy / Dominion Energy | 0.8138 NEE shares (+ small cash payment) | $65.84 | $67.90 | 3.1% |
| Sun Pharma / Organon | $14.00 cash | $13.78 | $14.00 | 1.6% |
Offer values for stock deals use the buyer's September 4 close: Union Pacific (UNP) at $289.62 and NextEra Energy (NEE) at $83.43 [6]. The NextEra figure excludes Dominion's share of the one-time $360 million cash payment [4].
Union Pacific and Norfolk Southern: a long regulatory road
Norfolk Southern (NSC) holders are to receive one Union Pacific share and $88.82 in cash per share, with about 72.2% of total consideration paid in stock [1]. Rail mergers need approval from the Surface Transportation Board (STB). The STB accepted the application but asked for more information, and on August 20, 2026 it adopted a procedural schedule in which comments from the Justice Department and Transportation Department are due December 3, 2026, rebuttals March 29, 2027, and final briefs May 28, 2027 [1][2]. A final decision will follow those briefs. A 14.9% spread with at least nine months of review ahead implies an annualized return near 18% if the deal closed by the end of June 2027. Returns that high signal meaningful doubt about approval, or about conditions that could reduce the value of the combination.
Paramount Skydance and Warner Bros. Discovery: litigation risk
Paramount Skydance (PSKY) agreed on February 27, 2026 to pay $31.00 per share in cash for Warner Bros. Discovery (WBD), an equity value of $80.9 billion, and to assume its net debt [3]. The deal faces two antitrust lawsuits: a private action filed in April 2026 and an action filed by twelve states in July 2026, in which the court granted a temporary restraining order on July 20 [3]. The parties agreed to postpone closing until the earlier of five days after the court's ruling or June 1, 2027 [3]. To compensate for delay, Paramount will pay a ticking fee of about $0.0028 per share per day after September 30, 2026 if the deal closes, and the agreement runs to March 4, 2027, with one automatic extension to June 4, 2027 [3]. If the deal closed on June 1, 2027, the 9.7% spread would equal about 13% a year before the ticking fee.
NextEra and Dominion, and Sun Pharma and Organon: lower risk, lower spreads
The NextEra and Dominion (D) all-stock merger needs shareholder votes and approvals from federal energy and nuclear regulators and three state utility commissions, and the companies expect it to close 12 to 18 months after the May 18 announcement [4]. Its 3.1% spread equals roughly 2.6% to 4.5% a year depending on the closing date. Organon (OGN) trades 1.6% below Sun Pharma's $14.00 cash offer; the companies expect closing in early 2027, subject to regulatory approvals [5]. That low spread signals strong confidence in completion.
How to read the probability inside a spread
A simple formula links price to probability. If the offer is worth O, the target trades at P and would fall to a fallback price F if the deal failed, the market-implied chance of success is (P minus F) divided by (O minus F). As an illustration only, if an investor assumed Warner Bros. Discovery would trade at $20 without a deal, a price of $28.25 against a $31.00 offer would imply about a 75% chance of completion. The fallback price is the hardest input to estimate, and different assumptions change the answer sharply.
- Time: longer reviews widen spreads even for deals likely to close.
- Regulatory and legal risk: lawsuits and sector regulators add uncertainty that is hard to diversify.
- Deal structure: stock deals require hedging the buyer's shares, and cash deals depend on financing.
- Downside: the gap between the offer and the fallback price sets how much can be lost.
Merger arbitrage also serves the market. By buying target shares from investors who do not want to wait, arbitrage funds provide liquidity and help prices reflect the likely outcome. Readers can follow pending transactions in DataPorium's M&A screener and check target and buyer prices on DataPorium's stock pages.
Merger arbitrage spreads in 2026 are wide where regulators or courts decide the outcome and narrow where closing looks routine.
Key takeaways
- As of September 4, 2026, gross spreads on large pending US deals ranged from 1.6% (Organon) to 14.9% (Norfolk Southern).
- The Union Pacific and Norfolk Southern spread reflects an STB schedule with final briefs due May 28, 2027.
- Warner Bros. Discovery trades 9.7% below Paramount's $31 cash offer while two antitrust lawsuits are pending.
- NextEra and Dominion's 3.1% spread reflects an all-stock deal expected to close 12 to 18 months after May 2026.
Frequently asked questions
What is merger arbitrage?
Merger arbitrage is buying the shares of a company being acquired at a price below the offer, and hedging the buyer's shares in a stock deal, to earn the spread if the deal closes. The main risk is a large loss if the deal fails.
Why is the Norfolk Southern merger spread so wide?
The Union Pacific deal needs Surface Transportation Board approval, and the board's schedule runs to final briefs on May 28, 2027. The 14.9% spread as of September 4, 2026 prices both the long wait and the risk that approval is denied or comes with costly conditions.
Will the Paramount and Warner Bros. Discovery deal close?
That depends on antitrust lawsuits, including one filed by twelve states. As of September 4, 2026, the stock traded 9.7% below the $31 offer, which suggests the market sees completion as likely but far from certain.
How do you calculate a merger arbitrage spread?
Subtract the target's share price from the value of the offer per share and divide by the target's price. For stock deals, the offer value equals the exchange ratio times the buyer's share price plus any cash.
Sources & References
- [1] Federal Register: STB, Union Pacific Control of Norfolk Southern (May 29, 2026)
- [2] Federal Register: STB Decision No. 30, procedural schedule (Aug 20, 2026)
- [3] Paramount Skydance Corporation Form 10-Q for the quarter ended June 30, 2026 (SEC EDGAR)
- [4] NextEra Energy newsroom: NextEra Energy and Dominion Energy to Combine, May 18, 2026
- [5] Organon: Sun Pharma signs Definitive Agreement to Acquire Organon, April 26, 2026
- [6] DataPorium Stock Market Data (daily closing prices, September 4, 2026)
