The Setup
When Company A announces acquisition of Company B at $50/share, and B's stock trades at $48, the $2 spread is the M&A arbitrage opportunity. If the deal closes as announced, you earn $2/share in 3-12 months.
Why Spreads Exist
- Some probability the deal breaks
- Time value of money (waiting for close)
- Regulatory / shareholder / financing risks
- Limited capital chasing the trade
Spreads implicitly price the market's estimate of deal failure probability.
Typical Spread Dynamics
Announcement spike
Stock moves from pre-announcement price toward (but below) deal price.
Narrowing through close
Spread tightens as deal-failure risks are resolved (regulatory approval, shareholder vote, financing commitment).
Blow-up
If the deal breaks, the stock usually collapses back toward pre-announcement price. Massive loss for arb traders.
Deal Types
Friendly / agreed deals
Both boards aligned. Highest close probability.
Hostile takeovers
Target board rejects initial offer. Often revised or abandoned. Wider spreads.
SPAC mergers
Different mechanics; SPAC redemptions drive much of the dynamic.
Stock-for-stock deals
Target gets acquirer shares, not cash. Arb requires simultaneously shorting acquirer to lock in spread (harder than cash deals).
Cash + stock hybrid
Combination of fixed cash and exchange ratio. Complex hedging.
Spread Size Implications
Narrow spread (1-3%)
Market sees high close probability. Lower return but safer.
Wide spread (5-15%+)
Market sees meaningful deal-break risk. Higher return but commensurate risk. Research required to understand why.
Very wide spread (20%+)
Something is very wrong. Regulatory block likely (antitrust), financing concerns, or target-board opposition.
The Three Main Risks
1. Regulatory
Antitrust (DOJ, FTC in US; European Commission; CMA UK; CNMC Spain). CFIUS for cross-border deals with US national security implications.
2022 example: Nvidia-Arm blocked by regulators. Arm reverted to IPO path instead.
2. Shareholder
Vote rejection (rare for friendly deals, common for hostile takeovers).
3. Financing
Acquirer needs to raise funds; if credit markets tighten, deals can be delayed or canceled.
How to Trade
Long target cash deals
Buy target stock; wait for close.
Long target / short acquirer stock deals
Simultaneously enter both legs at the exchange ratio.
Options strategies
- Buy calls on target for leveraged upside
- Sell puts on target for yield if bullish on close probability
- Manage gamma risk as spread narrows
Position Sizing
- Professional arb funds diversify across 20-50 deals
- Retail investors should not concentrate single deals
- Deal-break loss often 20-40%; size so any single failure isn't catastrophic
Research Process
Read the merger agreement
Material Adverse Change (MAC) clauses, breakup fees, financing conditions.
Regulatory review timeline
Check which antitrust authorities have jurisdiction. 6-18 month timelines common.
Proxy filings
Details the financial model, financial advisor's fairness opinion, and board deliberations.
Compare to historical deal-break rates
Base rate for friendly deals clearing HSR: ~95%+. Hostile deals much lower.
Common Mistakes
Ignoring regulatory calendar
A deal that closes in month 6 is very different from one that closes in month 18. Tax + time value matters.
Over-concentrating on one deal
A single deal-break can wipe out a year of arb returns.
Ignoring breakup fees
If acquirer walks, how much does target receive? Affects downside in break scenarios.
Hedging incorrectly in stock deals
Target / acquirer hedge ratio drifts if exchange ratio is based on a collar.
When to Close
- After close (automatic)
- Before close if spread has narrowed to <1% with regulatory clearance
- If break risk has risen materially (new regulatory concerns)
Key Takeaways
- M&A arbitrage = capturing spread between deal price and current trading price
- Spread size reflects deal-failure probability
- Main risks: regulatory, shareholder, financing
- Diversify across deals; don't concentrate single risk
- Read merger agreement; know breakup fees
See [/topic/mergers-acquisitions](/topic/mergers-acquisitions) for live M&A news.