HSR Merger Review Calendar in Flux After Court Vacates Filing Rule

The Hart-Scott-Rodino premerger notification program processed 203 transactions in March 2026, the highest monthly total since December 2025's 232 and a figure that would have been unremarkable just eighteen months ago, according to data compiled by HaystackID and published on JD Supra. The number landed in the same month that a federal court vacated the Federal Trade Commission's sweeping overhaul of the HSR filing form, an expansion that had, since its brief implementation, required merging parties to disclose organizational charts, narrative competition assessments, and documents from deal-team supervisors that prior rules had never demanded.

The court's decision, reported by Akerman LLP on JD Supra, materially reduced filing burdens for reportable transactions and threw the agencies back onto a form whose architecture dates to the pre-internet era. The practical consequence was immediate: deals that had been held in a holding pattern while practitioners puzzled through the expanded requirements could now proceed under the familiar, if antiquated, framework. The 203 filings in March reflect, in part, that release of pent-up deal flow.

The vacated rule had been the most consequential regulatory revision to the HSR process since the 1976 statute was amended to establish the modern premerger notification regime. It required filers to submit a narrative describing the competitive rationale for the transaction, supply documents prepared by or for the supervisory deal team lead, and disclose prior acquisitions in overlapping product markets. For transactions involving vertical or adjacent relationships, the demands grew steeper still. The U.S. Chamber of Commerce and a coalition of business groups had challenged the rule almost immediately after its finalization, arguing the FTC had exceeded its statutory authority under the Administrative Procedure Act.

On March 25, 2026, twelve days before HaystackID published its March filing tally, the Department of Justice Antitrust Division and the FTC issued a joint Request for Information seeking public comment on the future of premerger notification, as first covered by Wiley Rein LLP on JD Supra. The RFI was a procedural acknowledgment that the court had not merely paused the expanded rule but had vacated it, sending the agencies back to the drawing board. The RFI asked, among other things, whether the agencies should pursue narrower revisions that might survive judicial scrutiny and whether certain industry-specific exemptions remained justified.

One exemption under particular scrutiny is the real estate carve-out. A separate Fried Frank client alert published on JD Supra noted that the agencies have signaled they are considering eliminating exemptions that currently shield most real estate transactions from mandatory notification. The comment deadline is May 26, 2026. Real estate investment trusts, private equity firms with significant property portfolios, and developers who have long operated outside the HSR perimeter are watching the deadline with an attention the sector has rarely paid to antitrust procedure.

The regulatory turmoil has coincided with leadership upheaval at the DOJ's Antitrust Division. Gail Slater, who had served as the assistant attorney general for antitrust since the beginning of the second Trump administration, announced her departure on February 11, 2026, Deadline reported. Slater exited after less than a year in the role, at a moment when the division was simultaneously preparing for the Live Nation-Ticketmaster antitrust trial and reviewing Netflix's proposed $83 billion acquisition of Warner Bros. Discovery.

The Netflix-WB review had already become a political flashpoint. The Wrap reported that Democratic lawmakers had demanded answers from the White House and Attorney General Pam Bondi after Netflix CEO Ted Sarandos was photographed arriving for meetings at the White House in late February. Clete Willems, Netflix's chief global affairs officer, characterized the DOJ investigation as "totally ordinary" in comments reported by The Wrap via Yahoo Finance, a description that antitrust practitioners on both sides of the deal found technically defensible but incomplete.

What made the investigation ordinary was the HSR calendar itself. The statute establishes a 30-day initial waiting period, during which the agencies may issue a Request for Additional Information, colloquially called a second request. The second request extends the waiting period and gives the reviewing agency time to assess whether the transaction would substantially lessen competition. For a deal of Netflix-WB's scale, multiple second requests across overlapping and adjacent markets would be the expected course. The departure of the division's Senate-confirmed chief in the middle of that process was not.

The significance of the HSR calendar, and the waiting period that sits at its center, was illustrated in plainer terms by two transactions that cleared their respective waiting periods in late April. On April 24, Merck announced that the HSR waiting period for its acquisition of Terns Pharmaceuticals had expired, according to a Business Wire release carried by the Joplin Globe. The expiration cleared a regulatory hurdle for a transaction in the mid-cap biopharmaceutical space, a category where HSR filings are frequent and the competitive analysis typically turns on pipeline overlap rather than market concentration in finished products.

Three days earlier, on April 21, the Federal Trade Commission granted early termination of the HSR waiting period for RB Global's acquisition of BigIron, an online auction platform for used construction and agricultural equipment. RB Global announced the early termination via Business Wire, carried by the Rutland Herald. Early termination is a procedural signal that the reviewing agency has concluded no further investigation is warranted within the initial waiting period. It is not an antitrust clearance on the merits, but for public companies managing deal timelines and financing contingencies, it functions as the nearest thing to a green light the HSR statute provides.

The contrast between the RB Global-BigIron early termination and the Netflix-WB second request process captures the dual nature of the HSR calendar as it currently operates. On one track, transactions in fragmented markets with no obvious horizontal concentration issue move through the pipeline in the statutorily prescribed 30 days or less. On the other track, transactions that raise vertical foreclosure concerns, data-accumulation theories, or nascent-competition arguments that the current Supreme Court has shown little appetite for endorsing sit in investigative limbo while the division decides whether to litigate.

What the agencies are asking

The March 25 RFI poses a set of questions that reveal the agencies' post-vacatur posture. The joint request solicits comment on whether the expanded form's documentary requirements should be preserved in some narrower form, whether the definition of "person" for HSR purposes should be amended to capture a broader set of entity types, and whether the transaction-size thresholds that determine reportability should be adjusted for inflation or restructured entirely. The RFI also invites comment on whether certain classes of transactions, such as those involving minority investments below a specified percentage, should be exempted from filing requirements, a question that cuts against the broader expansionist impulse the agencies had pursued.

For the deal bar, the RFI represents both an opportunity and a risk. The opportunity is to shape a replacement rule that avoids the administrative overreach that doomed its predecessor. The risk is that the agencies, stung by the judicial vacatur, will pursue a narrower but still burdensome rule that manages to survive APA review while imposing costs nearly as high as the version the court rejected. Law firms with active M&A practices, including the several that published the analyses cited throughout this article, have been preparing comments that argue for calibrated disclosure requirements tied to transaction size and the degree of horizontal overlap.

What to watch for

The May 26 comment deadline is the next hard date on the HSR calendar. After that, the agencies will need to decide whether to propose a new rule, appeal the vacatur, or accept the reversion to the pre-expansion form as the indefinite status quo. The antitrust division will also need a new Senate-confirmed chief, and the identity of that nominee will signal how the administration intends to balance the procedural demands of the HSR calendar against the substantive enforcement priorities that the Slater tenure left unresolved. For dealmakers who spent the winter of 2025-2026 navigating the expanded form, the spring of 2026 has offered relief, but not clarity. The calendar is open. The rules are not.