What are the Requirements of an HSR Antitrust Filing for a Merger or Acquisition?
July 30, 2026
In the United States, mergers and acquisitions involving companies of a certain size must be reviewed by one of the competition authorities—the Federal Trade Commission or the Department of Justice.
Under 15 U.S.C. § 18a, commonly known as the Hart-Scott-Rodino Antitrust Improvements Act, parties to certain mergers and acquisitions must submit premerger notification filings known as HSR filings and wait a prescribed amount of time before consummating the transaction.
Bona Law has several attorneys who are experts on antitrust merger issues, and we handle transactions across a range of industries. Please contact us if you would like to speak with any of our attorneys about your transaction.
You should also check out these articles on antitrust, HSR filings, and mergers:
1. A $12 Million Lesson in HSR Rule 801.90: Purpose is the Whole Ballgame
2. Antitrust HSR Update: What the 55 Comments Tell Us About the Next Form
3. How to Run the Antitrust HSR Process When Your CEO is Impatient
4. HSR Update: Old, Shorter Form Likely in Use Through At Least 2026
5. HSR in Turmoil: Back to the Old Form, at Least For Now
6. U.S. Antitrust Agency Publishes Revised HSR Notification Thresholds and Filing Fees For 2026
7. California’s “Mini-HSR” Antitrust Filing Arrives in 2027: A Practical Compliance Checklist
10. How to Avoid an HSR Second Request (Maybe)
11. An Antitrust Agency Just Called About a Merger—What Happens Next?
12. Give and Take of Proposed HSR Rules: Private Equity Companies and Small Transactions
Below are some frequently asked questions with answers about HSR filings.
How is a Merger Defined for Antitrust Purposes?
For antitrust purposes, a “merger” includes any acquisition of assets, stock, or share capital of another person or entity, even if the acquisition does not result in control of the target company. An acquisition of less than a controlling interest does not obviate HSR filing requirements if the acquisition exceeds the operative thresholds. For the other terms of art you are likely to encounter during merger review, see our Glossary of Key Antitrust Terms.
What are the Relevant Thresholds That Trigger HSR Filing Requirements?
The HSR Act notification requirements apply to transactions that satisfy the specified “size of transaction” and “size of person” thresholds. These thresholds are adjusted annually to reflect changes in the U.S. gross national product. Three thresholds determine the applicability of HSR filing requirements.
First, one of the parties to the transaction must be engaged in commerce in the United States or in any activity affecting U.S. commerce.
Second, the acquiring party must be acquiring securities, non-corporate interests, or assets of the target in excess of $133.9 million—the “size of transaction” threshold. An HSR Act notification is not required when the value of the voting securities and assets is below this threshold.
Third, if the transaction exceeds $133.9 million but does not exceed $535.5 million, the “size of person” threshold applies: one party’s “ultimate parent entity” must have annual net sales or total assets of at least $267.8 million, and the other party’s “ultimate parent entity” must have annual net sales or total assets of at least $26.8 million.
Transactions valued at more than $535.5 million are reportable regardless of the size of the parties, unless an HSR Act exemption applies. The current thresholds remain in effect until the next annual adjustment, in the first quarter of 2027.
HSR Violations
Parties who violate the HSR Act are subject to monetary penalties. The maximum civil penalty for HSR Act violations is $53,088 per day for each day a party is in violation.
Revised Thresholds for Interlocking Directorates
The FTC has also adjusted the thresholds in Section 8 of the Clayton Act that trigger the prohibition on “interlocking directorates”—certain overlapping memberships on competitors’ boards of directors. They are now $54,402,000 for Section 8(a)(1) and $5,440,200 for Section 8(a)(2)(A).
What are the HSR Filing Requirements?
HSR filings are premerger notifications that parties to a proposed merger transaction make with both the Federal Trade Commission and the Department of Justice. Subject to minor exceptions, the seller and the buyer must each file separately with both agencies. Once the filing is made, a mandatory waiting period begins.
What Agencies Have Jurisdiction Over HSR Filings?
Both the U.S. Department of Justice and the Federal Trade Commission have jurisdiction over HSR filings. Because either agency may choose to review a merger, parties must submit HSR filings to both agencies.
When Does the Mandatory Waiting Period Begin?
The HSR waiting period begins the day after both the FTC and DOJ receive complete HSR filings from both the buyer and the seller of the transaction (for most filings). If one of the filings is not deemed complete, it may be “bounced,” and the waiting period is delayed until the deficiencies identified by the agency are corrected.
How Long is the Waiting Period?
For most filings, the mandatory initial waiting period is 30 days, beginning the day after the filings are received complete and ending at 11:59 p.m. on the 30th day thereafter (unless a federal holiday falls on either date).
If an agency makes a request for additional information (a “Second Request”), the transaction may not be consummated at the expiration of the initial waiting period. Typically, Second Requests are issued on the last day before the expiration of the initial waiting period.
What Happens During the Waiting Period?
During the waiting period, an agency will review the filing. If the agency decides not to take further action, it will do nothing and, when the waiting period expires, the parties are free to consummate the transaction. The agency may also grant an “early termination,” discussed below.
If an agency decides to conduct further review, it will issue a request for additional information called a “Second Request.”
Can We Do Anything to Speed It Up?
Either party may request “early termination” (ET) of the waiting period. Only one party to the transaction need request ET, but both agencies must grant the request for it to apply. ET may be requested in an HSR filing or made by separate request after filing. Because the agencies work on different timelines, one agency may grant it long before the other. And because the agencies are independent, one agency may grant ET but not the other. For these reasons, parties should not rely on the possibility of ET.
Update: The FTC and DOJ suspended early termination in February 2021 and reinstated it in February 2025 (announced October 10, 2024). Early termination is again available, though the agencies grant it less often than they did historically.
What Happens After a Second Request?
If an agency makes a Second Request, the parties must attempt to “substantially comply” with the request. Once the parties comply and submit valid certifications of substantial compliance, the waiting period ends 30 days after the date of the certification. Substantial compliance is a significant undertaking, which is why it is worth planning early to avoid a Second Request in the first place.
If Consummation is Delayed, How Long is the HSR Filing Valid?
Once a transaction’s waiting period expires, the acquiring party has exactly one year from that date to consummate the transaction, regardless of whether that date falls on a weekend or holiday. After one year, the HSR filing is expired, and the parties must submit new HSR filings.
What Can We Do to Run More Time?
Acquiring parties seeking to run more time may “withdraw and refile” an HSR filing without paying a new filing fee, which starts a new waiting period. This can benefit both the filing parties and the agencies because it can allow agencies to timely review the transaction without issuing a Second Request. The withdraw-and-refile process is not available if a Second Request has already been issued.
Important 2026 Development
In early 2025, the FTC adopted the most significant overhaul of the HSR premerger notification form since 1976, sharply expanding the information required at filing. The business community challenged the rule.
On February 12, 2026, a federal court in the Eastern District of Texas vacated the rule in full, finding that the agency had not shown the new requirements were necessary and appropriate and had not adequately weighed costs and benefits.
On March 19, 2026, the Fifth Circuit denied the FTC’s motion to stay that decision. The FTC returned to the pre-2025 form and announced it would accept the old form going forward, while continuing to accept the new form for parties who prefer to use it. The merits appeal remains pending, so the rules could change again. HSR thresholds, reportability tests, and statutory waiting periods are unaffected.
For more detail, see HSR in Turmoil: Back to the Old Form, at Least For Now and HSR Update: Old, Shorter Form Likely in Use Through At Least 2026.