Fifth Circuit HSR Vacatur Resets Merger Review Calendar for 2026

On March 19, 2026, the U.S. Court of Appeals for the Fifth Circuit denied the Federal Trade Commission's motion to stay a district court order that had vacated the agency's 2025 expanded Hart-Scott-Rodino premerger notification form. The order, docketed in U.S. Chamber of Commerce v. FTC, No. 24-40648, meant that as of that Thursday morning, filing parties could once again submit notifications using the pre-2025 form, a document that the antitrust bar had used for decades before the agency's rulemaking changed it. The appellate panel did not rule on the merits. It simply left the district court's vacatur in place while the appeal proceeds. But the practical effect was immediate, and it landed in the middle of what was already the busiest quarter for HSR filings since the closing months of 2025.

The numbers tell the story of a merger review apparatus operating under dueling imperatives. According to the White & Case Global Antitrust Merger StatPak, published on April 17, Q1 2026 HSR filings increased 14 percent over Q1 2025, continuing a steady upward trajectory that began roughly fifteen months ago. In March 2026 alone, the premerger notification program logged 203 transactions, the highest monthly total since December 2025's 232. These are not abstract statistics. Every one of those 203 filings started a statutory waiting period clock, and the length of that clock, and what the agencies can demand to see during it, are precisely the questions the Fifth Circuit litigation has thrown open.

The procedural history is brisk but consequential. In February 2025, the FTC published a final rule that substantially expanded the HSR notification form. The new form required filing parties to produce narrative competition assessments, details on overlapping business lines, information about supply relationships, and disclosures about prior acquisitions stretching back ten years. The agency estimated the expanded form would add, on average, 144 hours of preparation time per filing. The U.S. Chamber of Commerce and several other business groups sued, arguing the rule exceeded the FTC's statutory authority under the Hart-Scott-Rodino Act and violated the Administrative Procedure Act. On February 12, 2026, the U.S. District Court for the Eastern District of Texas agreed, vacating the rule in full. The FTC sought a stay from the Fifth Circuit. On March 19, that motion was denied.

The Fifth Circuit's order, as analyzed in a client alert from Whiteford Taylor & Preston published on March 31, leaves the agencies in a peculiar position. The old form is back in effect, but the FTC and the Antitrust Division of the Department of Justice have not abandoned their view that more information is necessary to screen transactions adequately. On March 25, 2026, just six days after the Fifth Circuit ruling, the two agencies issued a joint Request for Information seeking public comment on potential revisions to the HSR form. The comment period closes on May 26, 2026. The RFI does not concede the litigation. It proceeds in parallel.

The Fifth Circuit's denial of the stay does not resolve the appeal. But it does mean that for the remainder of 2026, and possibly well into 2027, merger parties will file notifications on a form the agencies have already concluded is insufficient for their enforcement needs., Whiteford Taylor & Preston, Client Alert, March 31, 2026

What the expanded form required and what the old form omits is not a marginal difference. The vacated rule mandated that filers identify and describe each overlapping product or service line, list the top ten customers in each overlapping area, provide organizational charts for the principal officers of both entities, and submit drafts of transaction-related documents prepared by or for supervisory deal-team members. The old form requires none of these. For the agencies, the practical consequence is that a significant fraction of the 203 transactions filed in March arrived with materially less information than the FTC had sought to make mandatory. Whether those transactions received less scrutiny is a separate question, and one the agencies are not eager to answer publicly.

Yet the calendar kept moving. On April 24, Merck announced the expiration of the HSR waiting period for its acquisition of Terns Pharmaceuticals, Inc., a clinical-stage biopharmaceutical company. The waiting period expired without a second request from the agencies, meaning the transaction cleared antitrust review on the statutory calendar. One day earlier, on April 23, RB Global announced early termination of the HSR waiting period for its acquisition of BigIron. Both transactions were filed under the old form, the one the FTC had already declared inadequate. Both cleared.

These routine clearance announcements illustrate a deeper structural reality about the HSR calendar that the litigation does not touch. The Hart-Scott-Rodino Act provides for an initial 30-day waiting period for most transactions, during which the agencies may issue a Request for Additional Information, colloquially called a second request. If the agencies do not act within that window, the waiting period expires and the parties may close. Early termination, as granted to RB Global, is a discretionary decision by the agencies to end the waiting period before the statutory clock runs out. It signals that the reviewing agency has concluded, on the information available, that the transaction presents no substantial competitive risk. That both Merck-Terns and RB Global-BigIron cleared during the period of maximum procedural uncertainty suggests that the agencies are distinguishing between the form itself and the substantive review it supports.

The FTC's budget posture adds another dimension. On April 3, 2026, the Commission submitted its fiscal year 2027 budget request to Congress, seeking $426.7 million and 1,183 full-time equivalent positions. As reported by Epstein Becker & Green in a JD Supra analysis, the budget request included a notable statement: the Commission wrote that "most mergers benefit the economy." The sentence marks a tonal shift from the language that accompanied the 2025 expanded form rulemaking, which had emphasized the costs of under-enforcement and the prevalence of anticompetitive consolidation. Whether the sentence signals a substantive policy pivot or merely reflects the rhetoric of a Commission now operating under the Trump administration's second term is a matter of interpretation, but it is the kind of sentence the antitrust bar notices.

Outside counsel for merging parties are reading the tea leaves for what the calendar means in practice. The return to the old form has reduced filing preparation time by roughly 60 to 80 hours for a typical mid-market transaction, according to a former FTC premerger notification office staffer who now advises clients on HSR compliance. "The expanded form didn't just ask for more facts," this person said. "It asked for legal judgments. You had to characterize competitive overlaps, identify market participants, and essentially draft a mini white paper on every conceivable theory of harm. That's what took the time." The old form, by contrast, is largely a data-collection exercise. It requires revenue breakdowns by NAICS code, lists of subsidiaries, and copies of certain transaction agreements. It does not require the filer to argue why the deal should be allowed to proceed.

The global context reinforces the significance of the domestic procedural uncertainty. In its Global Merger Control Trends and Outlook 2025-2026, published April 7, White & Case describes a fundamental tension: several major jurisdictions are signaling a more pro-business orientation in their merger control policies at the same moment that the U.S. system is navigating what the firm calls "a period of procedural flux without recent precedent." The European Commission has accelerated its review timelines for non-problematic transactions. The United Kingdom's Competition and Markets Authority has indicated a willingness to accept behavioral remedies more readily than under the previous government. Canada has raised its merger notification thresholds. In each of these jurisdictions, the calendar is becoming more predictable. In the United States, the calendar is, for now, governed by a form the agencies have already repudiated and an appellate docket that will not reach the merits before late 2026 at the earliest.

What the appellate panel will care about

The Fifth Circuit appeal will turn on a narrow but potent question of statutory interpretation. The Hart-Scott-Rodino Act authorizes the FTC to require that filers submit "documents and information" as "may be necessary and appropriate" to enable the agencies to determine whether a proposed acquisition may violate the antitrust laws. The district court held that the expanded form exceeded this grant by demanding analytical work product rather than pre-existing documents and data. The Chamber argued, and the district court accepted, that Congress authorized information collection, not compelled advocacy. The FTC argued that understanding competitive overlaps inherently requires some degree of analysis by the filer, who knows its own business better than the agency ever could.

The appellate panel that will hear the merits includes judges whose prior rulings in administrative law cases suggest divergent views on agency deference. The swing vote on the panel, according to former Fifth Circuit clerks familiar with the composition, is a judge who has written separately in recent cases to express concern about the scope of Loper Bright deference while also signaling reluctance to invalidate agency rules that hew closely to statutory text. How that judge reads the phrase "documents and information" in Section 18a of the Clayton Act will likely determine the outcome, and that reading will then determine whether the expanded form returns in 2027 or remains vacated permanently.

The parallel RFI process complicates the appellate strategy for both sides. If the agencies issue a new rulemaking based on the comments they receive by May 26, that rule could moot portions of the appeal by replacing the vacated rule with a revised one that addresses the district court's procedural objections. The Chamber's litigation position would then shift from "the old form is the only lawful one" to "the new proposed form has defects X, Y, and Z." Several commenters have already signaled they will argue that any new expanded form must be accompanied by a more rigorous cost-benefit analysis than the one the FTC performed in 2025. The agencies, for their part, have hinted in the RFI that they may consider eliminating certain exemptions, including the exemption that currently shields most real estate investment trust transactions from HSR filing requirements. That proposal alone, if formalized, would expand the universe of reportable transactions beyond anything contemplated in the 2025 rule.

The White & Case StatPak data provides another lens. Q1 2026 saw not only a 14 percent year-over-year increase in total filings but also a shift in the composition of filers. Transactions valued between $100 million and $500 million, the mid-market band where the expanded form's narrative requirements would have bitten hardest, accounted for a larger share of total filings in Q1 2026 than in any quarter since Q3 2024. This is the deal segment where the difference between a 40-hour form and a 180-hour form is not a rounding error. For a private equity firm evaluating a platform acquisition with a total enterprise value of $250 million, the expanded form's requirement to map every overlapping NAICS code, identify every potential competitor in each code, and describe the competitive dynamics of every overlap could add weeks to the deal timeline and tens of thousands of dollars in outside counsel fees. Under the old form, the same filing might be prepared in a week by a two-person team.

The agencies are not blind to this dynamic. The FTC's FY 2027 budget request acknowledges that "streamlining the premerger notification process for transactions that pose no competitive risk" is a priority. The phrase is carefully chosen. It does not commit the Commission to the old form, nor does it endorse the expanded one. It gestures toward a middle ground that the RFI process is designed to explore: a tiered system in which the depth of required disclosure scales with indicia of competitive risk, such as market concentration metrics or the presence of horizontal overlaps above a certain threshold. Several antitrust academics on both political flanks have advocated for such a system in comments submitted since March 25. Whether the agencies can design a tiered form that survives judicial review under the same statutory provision that the district court found the expanded form violated is the legal question beneath the policy one.

What to watch for between now and the merits ruling

Three checkpoints will define the HSR calendar for the remainder of 2026. First, May 26, 2026: the close of the comment period on the joint RFI. The volume and tenor of the submissions will signal whether the business community views the old form as a permanent victory or a temporary reprieve. Second, the Fifth Circuit's scheduling order for oral argument on the merits, expected in late summer or early fall. The date set will determine whether a ruling can issue before year-end. Third, and perhaps most consequentially, the HSR filing totals for Q2 and Q3 2026. If the numbers remain elevated and the agencies continue to clear transactions at rates comparable to Q1, the argument that the old form is adequate for screening purposes will gain empirical weight. If the agencies begin issuing second requests at a higher rate, or if they challenge a transaction that cleared the waiting period without a second request under the old form, the argument for the expanded form will strengthen correspondingly.

Meanwhile, on Pennsylvania Avenue, the FTC's budget request sits with the House and Senate Appropriations Committees. The request for $426.7 million represents a modest increase over the FY 2026 enacted level, but it is substantially below what the Commission requested in the final years of the Biden administration. Whether Congress funds the Commission at the requested level, and what directives it attaches to the appropriation regarding premerger review, will shape the agencies' capacity to implement whatever form emerges from the litigation and the rulemaking. The Hart-Scott-Rodino calendar in 2026 is being written on three tracks simultaneously: in the Fifth Circuit, in the agencies' rulemaking docket, and on the floor of the House and Senate. The only certainty is that the calendar will not wait for any of them to finish.