HSR Filings Surge to 203 in March After Court Vacates FTC Rules

On March 19, 2026, the United States Court of Appeals for the Fifth Circuit denied the Federal Trade Commission's motion for a stay pending appeal in U.S. Chamber of Commerce v. FTC, No. 25-10001 (5th Cir.). The panel's one-paragraph order meant that a district court ruling vacating the FTC's 2024 overhaul of the Hart-Scott-Rodino premerger notification rules would remain in effect while the government's appeal proceeded. For merging parties, the practical consequence was immediate: the old HSR form, the one that had governed premerger filings from 1978 until January 2025, was back. The expanded form, which had required filers to submit narrative competition analyses, internal deal documents, and detailed labor-market overlays, was no longer the law of the land.

The calendar moved fast after that. According to data published by e-discovery firm HaystackID on JD Supra, the premerger notification program logged 203 transactions in March 2026, the highest monthly total since December 2025's 232 and a figure that would have been unremarkable just 18 months earlier but that now registered as a signal. The reversion to the prior form cut the average filing burden from roughly 144 hours of preparation back to 37 hours, by the FTC's own earlier estimates, and dealmakers who had been waiting on the sidelines for the litigation to resolve moved transactions into the queue.

The HSR calendar operates on a simple mechanical premise: a transaction that meets certain size thresholds must be reported to the FTC and the Department of Justice's Antitrust Division, and the parties must then observe a statutory waiting period, typically 30 days for most transactions, before they may close. During that window the agencies may issue a second request, which extends the waiting period and demands substantial additional documentary production. The waiting period is the clock that structures every significant U.S. merger timeline. When the expanded form was in effect between January 2025 and February 2026, practitioners reported that the preparation burden had effectively added weeks to the pre-filing phase, compressing the time available for agency review before the parties could close.

The district court vacated the expanded rules on February 13, 2026, in the Northern District of Texas. Judge Reed O'Connor held that the FTC failed to conduct a proper cost-benefit analysis under the Administrative Procedure Act before imposing what the Chamber of Commerce and other plaintiffs characterized as the most significant expansion of HSR filing requirements in the statute's history. The court did not reach the question of whether the FTC had the statutory authority to demand the new categories of information; it held only that the agency had not adequately justified the rule under the APA's arbitrary-and-capricious standard. The ruling, reported by multiple firms on JD Supra, left open the possibility that a properly supported rule could survive judicial review.

The Fifth Circuit's refusal to stay the vacatur pending appeal accelerated the timeline. Three days after the appellate ruling, on March 22, the FTC published a Federal Register notice formally reinstating the prior HSR rules and the prior form. The notice was remarkable for its brevity: the agency stated that it was complying with the court's order and that the prior rules were in effect as of that date. It did not concede the legal arguments. It did not preview an appeal strategy. It simply pointed filers back to the instructions they had used for 47 years.

For in-house M&A counsel, the reversion compressed the pre-filing timeline in ways that rippled through deal calendars across the spring. A transaction that had been budgeted for six to eight weeks of HSR preparation under the expanded regime could, under the old form, realistically be filed in two to three weeks. The 30-day statutory clock started earlier, and the agencies had not yet signaled whether they would use the freed-up investigatory bandwidth to issue more second requests or to clear more transactions within the initial waiting period.

Two deals, two waiting periods, one calendar

On April 21, 2026, the FTC granted early termination of the HSR waiting period for RB Global's acquisition of BigIron, an online auction platform for used farm and construction equipment. RB Global, a publicly traded company that operates the Ritchie Bros. auction brand, announced the early termination on April 23, confirming that the transaction had cleared HSR review well before the 30-day clock expired. Early termination is a discretionary action: the agencies grant it when they determine that the transaction raises no competitive concerns and that no further investigation is warranted. It is, in effect, a signal that the deal is unremarkable from an antitrust perspective.

The following day, April 24, Merck announced that the HSR waiting period had expired for its acquisition of Terns Pharmaceuticals, a clinical-stage biopharmaceutical company focused on oncology. Merck used the standard formulation: the waiting period had expired, meaning the full 30 days had run, and the agencies had neither issued a second request nor sought to extend the review. For a transaction in a pharmaceutical sector that has drawn heightened antitrust scrutiny in recent years, the quiet expiration was itself newsworthy. It suggested that the FTC and DOJ, now operating under the Trump administration's more permissive merger enforcement posture, did not view a large pharma acquisition of a pipeline-stage biotech as presumptively problematic.

These two filings, one drawing early termination and the other drawing a quiet expiration, illustrate the spectrum of outcomes that the HSR calendar produces for deals that raise no immediate red flags. Neither transaction required the parties to negotiate a consent decree. Neither required a second request. Neither triggered the extended investigatory timeline that has become more common in tech and platform-market deals. The calendar worked as designed: file, wait, clear, close.

What the agencies are saying, and what they are not

On March 25, 2026, less than a week after the Fifth Circuit's denial, the FTC and the DOJ Antitrust Division issued a joint Request for Information seeking public comment on the future of the HSR premerger notification form. The RFI, published in the Federal Register and summarized by Wiley Rein LLP on JD Supra, asked a series of open-ended questions: What information should a revised HSR form collect? How should the agencies balance the burden on filers against the need for early-stage competitive analysis? Should the form differentiate between categories of transactions based on size or sector? The comment deadline was set for May 26, 2026.

The RFI was notable for what it did not do. It did not propose a new rule. It did not preview specific regulatory text. It did not commit the agencies to any particular timeline. It was, in substance, a reset: after the judicial rebuke, the agencies were asking stakeholders to help them build a record that could support whatever rulemaking came next. Antitrust practitioners read the RFI as an implicit acknowledgment that the vacated rule had been built on a record too thin to survive an APA challenge and that the next attempt would need to be heavier on economic evidence and lighter on regulatory ambition.

The RFI arrived against the backdrop of the FTC's fiscal year 2027 budget request, submitted to Congress on April 3, 2026. The request sought $426.7 million and 1,183 full-time equivalents, a figure that represented a modest increase from the previous year. More significant than the number was the accompanying language. As Epstein Becker and Green noted on JD Supra, the FTC's budget submission stated that "most mergers benefit the economy" and emphasized the agency's commitment to a "balanced approach" that would "welcome procompetitive consolidation" while targeting transactions that harm competition. The language was a departure from the rhetoric of the prior administration, which had framed merger enforcement in more adversarial terms, and it signaled that the Commission under Chairman Andrew Ferguson intended to calibrate HSR review in a more business-friendly direction.

Most mergers benefit the economy. The Commission's merger enforcement program should distinguish between transactions that harm competition and those that enhance it, and should allocate resources accordingly., Federal Trade Commission, Fiscal Year 2027 Budget Request to Congress, April 3, 2026

This language matters for the HSR calendar because it signals resource allocation. The agencies have finite staff to review the thousands of HSR filings they receive each year. If the Commission's default posture is that most mergers are benign, then fewer transactions will draw second requests, fewer second requests will lead to enforcement actions, and the average deal will spend less time in regulatory limbo. The calendar, in short, will shorten for most filers.

The broader global context reinforces this domestic trajectory. The Global Merger Control Trends and Outlook 2025-2026 report published on JD Supra in early April described a "fundamental tension" in international merger control: several major jurisdictions, including the United Kingdom under its new government and the European Union under its revised merger guidelines, signaled a more interventionist posture, while the United States under the Trump administration moved in the opposite direction. The report noted that the divergence was creating a "bifurcated global M&A landscape" in which the same transaction might face a 30-day clearance in Washington and a six-month Phase II investigation in Brussels.

The Netflix-Warner Bros. Discovery transaction, an $83 billion combination that the Department of Justice began investigating in early 2026, illustrates the high-stakes end of this divergence. Netflix's chief global affairs officer, Clete Willems, told the Senate Judiciary Subcommittee in February that the investigation was "totally ordinary" and that the company was cooperating fully. That deal, reported by The Wrap via Yahoo Finance, is likely to test whether the Trump administration's permissive rhetoric translates into permissive outcomes when the transaction is large enough, in a concentrated enough sector, to draw sustained public attention. The HSR calendar is designed for exactly this kind of transaction: a filing triggers the 30-day clock, a second request extends it, and the real regulatory work happens in the months that follow.

What happens next on the HSR calendar itself depends on three variables. The first is the Fifth Circuit's ruling on the merits of the government's appeal. Oral argument has not yet been scheduled, and the case could take a year or more to resolve. During that period, the old form remains in effect, and the filing surge that began in March will continue. The second variable is the RFI process. If the agencies receive substantial, detailed comments from stakeholders, they may propose a revised rule that addresses the district court's cost-benefit concerns without retreating to the pre-2025 status quo ante. A notice of proposed rulemaking could appear as early as the fourth quarter of 2026. The third variable is the political calendar: a change in administration in 2028 could reverse the enforcement posture again, making the current period of relative permissiveness a window that dealmakers are motivated to use.

The HSR program is one of the quieter pieces of federal regulatory infrastructure. It operates through forms and waiting periods and Federal Register notices, not through high-profile court arguments or consent-decree negotiations. But in 2026, the calendar itself has become the story. A court vacated the rules that governed it. Filings spiked. The agencies asked for public input on what should come next. And dealmakers, watching the clock, moved their transactions into the queue while the old form remained available. The May 26 comment deadline on the RFI is the next checkpoint. What the agencies do with those comments will determine whether the HSR calendar in 2027 looks like the one from 2024 or the one from 2025, or something the agency has not yet imagined.