Ending the Inevitable Eleventh-Hour Scramble: Why the New HSR Rules Demand Earlier Economist Engagement
I. The “eleventh hour” agency call under the previous regime.
Every seasoned M&A practitioner knows the scenario well. Two, sometimes three, weeks into the 30-day HSR waiting period, the email arrives or the phone rings. It is the investigating agency and they have questions. This moment has long triggered a familiar, frenetic scramble to respond to inquiries that can feel like they have come out of left field. An agency economist may join the call, request specific cuts of data, or raise unanticipated theories of harm, which injects significant uncertainty into a tightly managed transaction timeline.
To be clear, the eleventh-hour nature of the calls was never because anyone was sitting on their hands with HSR filings. Instead it usually reflects the reality that staff has far fewer than 30 days to review the filing, given the necessary lead times for the preparation of internal recommendations.[1] This is a condensed timeframe in which staff attorneys and economists could review the filing and request additional data and information needed to begin a substantive review.
Although outside counsel often preempt this call with proactive outreach, many deals—especially those with less obvious competitive issues—could become caught in a reactive cycle. This period of intense, time-sensitive work, even when expertly navigated, still introduces a substantial risk to transaction timelines and, perhaps most importantly, can place a heavy burden on business-side personnel.
II. Recent HSR filing rule changes require more information, documents, and data be provided with the initial filing.
The recent amendments to the HSR filing requirements alter the timeline of an antitrust investigation, effectively moving some of the steps that once occurred during the initial 30-day waiting period to the pre-filing stage. This presents an opportunity for a more proactive approach that is expected to decrease the frequency of eleventh-hour calls from the agencies, although it may not eliminate them in all cases. As an example, the merger parties must now provide a description of overlapping products and/or services in their initial filing (Final Rule, p.89371-72), and must also submit sales and customer data for the products or services identified as overlaps. Because these descriptions can lead to significant impacts on advocacy plans, securing economist help to think through the best way to frame those descriptions may be crucial. Although the filing should not include any advocacy, [2] the data and information included will form part of the agency review. It will be important, therefore, that the parties’ plan for advocacy aligns with the information they provide in their initial filing.
Previously, the process was more reactive. While parties had the option to voluntarily provide this type of data and analysis early in the waiting period, it was more common for them to wait. Parties often supplied this information only after agency staff and economists formally requested it through what are known as Voluntary Access Letters (VALs). Because these requests for information would be issued well into the 30-day waiting period, this contributed to the eleventh-hour timing of follow-up calls and meetings.
The new rules address this procedural delay directly, making it less likely that such calls will be necessary for a subset of deals.[3] My own experience providing economic support aligns with this; many transactions I have worked on were assessed as posing minimal risk to competition, but their inherent complexities—either in the deal structure or the markets involved—required more time for agency staff to fully understand and evaluate.
Requiring this critical information in the initial HSR filing creates the potential to bypass the later step of issuing a VAL. For these types of complex but ultimately non-problematic deals, this change can effectively fast-forward the agency's review, leading to a more efficient and predictable process.
III. The new HSR data correlates to key economic issues in merger review.
The questions and information reflected in the new HSR rules are the product of the agencies’ years of experience reviewing deals and asking questions. The issues being addressed are recognizable to those of us with experience in merger review at antitrust agencies; these are the basic questions and data requests that regularly come up.
As a result, an advanced understanding of how an agency economist will likely receive and interpret the information in your filing confers a significant strategic advantage. It allows a company to anticipate concerns, then craft more effective economic and legal arguments, and, ultimately, address potential issues more efficiently. This proactive approach greatly improves the likelihood of a shorter, less intensive review. This principle is especially true for the newly expanded document requirements, which, as former senior agency officials have noted, are likely to surface key internal documents—the kind that previously might only have been obtained after the issuance of a burdensome Second Request.[4]
There are clear “through-lines” from the new filing requirements to the analytical frameworks the agencies apply, which are detailed in the 2023 Merger Guidelines. For example, the detailed information now required for supply agreements directly tracks with the framework of Guideline 5. This is the guideline which explains how the agencies assess deals that combine firms in the same supply chain for risks of vertical foreclosure—where the merged firm might use its control over a key input or customer channel to harm its rivals.
Although transactions that pose a serious vertical foreclosure risk are relatively uncommon, the newly mandated data on supply relationships gives the agencies the ability to perform a quick initial screen. Using a calculation known as “vertical math,” an agency economist can analyze the submitted data to assess whether the transaction could create the ability and incentive to harm rivals. Although this initial calculation is not definitive, it can serve as an important first pass that helps the agency decide whether a deeper, more comprehensive review of the transaction is warranted.
The new data requirements can provide a window into other key competitive issues as well. For example, the Merger Guidelines describe market definition analyses such as “Recapture Rate” and “Critical Loss” (Section 4.3). High-level versions of these calculations may be possible with the data and documents included in many filings, giving directional guidance on potential market definition. In another area, evaluating of the risk that a transaction’s eliminates a potential entrant, an analysis described in Guideline 4, may now be supported by the data and information included with some filings on “known planned” overlapping products and services.
Although these examples confirm why engaging economists has always been a valuable strategy, the new HSR rules make their early involvement indispensable. Because the data and information now required at the time of filing can be so influential in how a deal may be reviewed, expert economic input is no longer a reactive measure, but a proactive necessity.
IV. Filers can translate the new HSR requirements into an advantage.
The new HSR requirements present a strategic opportunity for filing parties. Even though the rules demand a more intensive upfront effort, they also create a clear path to a more predictable and efficient agency review. Engaging an experienced economist to advise on the preparation of the HSR filing is a key means for parties to capitalize on this opportunity. Given the longer preparation time that is now expected for many transactions, a focused, narrowly scoped economic engagement is a high-value means to leverage that additional time. To help frame overlap or supply relationship descriptions, for example, an economist is likely to only need access to some ordinary course documents and answers to a discrete set of questions.
The benefits of this early economic involvement can be substantial. They manifest as both a reduction in regulatory uncertainty at the outset of a deal and a decrease in the overall costs required to see the agency’s review through to a conclusion. These latter costs are not just financial; they include the significant time and stress sometimes imposed on the employees of the businesses who necessarily field time-sensitive requests. Reducing such risks can have indirect, yet meaningful, impacts on general business operations and morale.
CITATIONS
[1] Making the Case for Your Deal, ABA Antitrust Law Section, Federal Civil Enforcement Committee Webinar, June 5 2025 (membership required) https://www.americanbar.org/groups/antitrust_law/resources/on-demand/making-the-case-for-your-deal/
[2] This is less likely to be true for very large deals or those occurring in sectors that agency officials have announced are a priority.
[3] In making the Final Rule, the FTC stated that “[t]he Commission intends to collect factual information about overlaps and supply relationships via a written answer (as opposed to documents or data) but is not seeking opinions or arguments about what those facts should imply.” p. 89310.
[4] The Hart-Scott-Rodino Antitrust Improvements 1976 Act (“HSR Act”) requires that parties to a merger meeting a monetary thresholds (most commonly the size of transaction threshold which is set at $126.4 million in 2025) report their transaction to the federal antitrust agencies, the Federal Trade Commission, and the Antitrust Division of the Department of Justice, and observe a 30 day waiting period after filing. The waiting period can conclude in one of several ways: 1. Expiration without action from the agency, 2. Early Termination by the agency at its discretion, or after substantial compliance with a Second Request that may be issued by the investigating agency (which can only be one or the other).
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