What Is the Hart-Scott-Rodino Act?
The Hart-Scott-Rodino Antitrust Improvements Act created the US premerger notification regime. Before HSR, antitrust agencies often had to challenge anticompetitive mergers after they closed, when unwinding them was messy or impossible. The act flipped the sequence: parties must tell the Federal Trade Commission and the Department of Justice about qualifying deals in advance and wait for review before completing them.
The core trigger is the size-of-transaction test, a threshold adjusted annually for economic growth that stood at roughly $126 million in 2025. Both the acquirer and the target submit filings, and the buyer pays a tiered filing fee that ranges from $30,000 on the smallest reportable deals to more than $2 million on transactions above $5 billion.
How the HSR Process Works
After the parties file, an initial waiting period of 30 days begins, shortened to 15 days for all-cash tender offers and certain bankruptcy sales. Most deals raise few competitive concerns and clear when the period expires. A rule overhaul that took effect in 2025 made the filing itself far more demanding, requiring narrative descriptions of competitive overlaps and broader document production up front.
If the agencies see potential harm to competition, they issue a Second Request, a sweeping demand for documents and data that pauses the clock until both parties substantially comply. That process can stretch for many months. From there, the parties may negotiate divestiture remedies or fight the agency in court, and some simply abandon the transaction rather than endure the battle.
Why HSR Matters in M&A
Merger agreements make HSR clearance a condition to closing, so antitrust risk shapes the outside date, the efforts covenants, and increasingly the reverse termination fee a buyer must pay if regulators block the deal. Bankers build these timelines into every process, because a deal expected to face a Second Request may take a year or more to close.
The act also polices behavior between signing and closing. Buyers who start operating the target early, a violation known as gun-jumping, face civil penalties that exceed $50,000 per day. For analysts and associates, tracking HSR filings and waiting periods is a routine part of managing a live deal, and understanding the process signals genuine M&A fluency in interviews.
