Could skipping an antitrust premerger notification filing cost your deal — and millions — later?
Under the Hart‑Scott‑Rodino Act, antitrust premerger notification rules force most big mergers to notify the FTC and DOJ before closing and sit through a waiting period while regulators review.
That filing controls timing, can prompt second requests, and carries daily penalties if ignored.
This post walks through the HSR thresholds and tests, required documents, waiting‑period strategies, and straightforward steps teams should take to stay compliant and avoid delays.

Core Framework of Federal Antitrust Premerger Notification Rules

The Hart-Scott-Rodino Act makes companies notify the FTC and DOJ before they can close mergers, acquisitions, or certain joint ventures above set dollar thresholds. Congress passed the HSR Act in 1976 so federal antitrust enforcers could see big transactions before they happened. The law creates a waiting period where agencies review what you filed, ask for more if they need it, and decide whether to block the deal. Both the FTC and DOJ enforce the rules. They split up the work internally through a clearance process.

The HSR Act has two tests: size of transaction and size of person. When a deal tops the transaction threshold (adjusted yearly for inflation, $126.4 million in 2025), both sides file unless an exemption applies. The size-of-person test means one party needs at least $252.8 million in annual net sales or total assets, and the other needs at least $25.3 million. Deals above $505.5 million? You file no matter how big or small the parties are. The waiting period is 30 days for most deals, 15 for cash tender offers. Reportable transactions cover voting securities, non-corporate interests like LLC membership units, and assets.

An HSR filing package usually has:

• Completed HSR form with detailed party and transaction info
• Org charts showing who owns and controls what
• Revenue broken down by NAICS code for overlapping products or services
• Item 4(c) documents: strategic plans, board decks, ordinary-course analyses prepared to evaluate the transaction
• Item 4(d) documents: studies, surveys, analyses made by or for officers or directors to assess markets, competition, competitors, or market shares
• Filing fee (tiered by deal value, from $30,000 to $2.3 million)

Several states now want copies of HSR filings under “mini-HSR” laws. Only the federal waiting period controls when you can close. State filings give state AGs early notice and access to otherwise-confidential HSR materials, but they don’t create extra waiting periods. You can close once the federal period ends or the agencies grant early termination, even if a state is still looking.

Transaction Thresholds and Tests Under Premerger Notification Rules

The size-of-transaction test measures the total value of voting securities, non-corporate interests, or assets you’ll hold after closing. The HSR statute sets a base threshold the FTC adjusts every January based on changes in U.S. gross national product. For deals above $126.4 million but at or below $505.5 million, both tests have to be satisfied. Above $505.5 million? Only the transaction threshold matters. The FTC publishes revised thresholds and fees in the Federal Register each year.

The size-of-person test requires one party to have annual net sales or total assets of at least $252.8 million, and the other to have at least $25.3 million. The test looks at the ultimate parent entities, not subsidiaries. You calculate annual net sales and total assets using the most recent regularly prepared balance sheet and income statement. When a deal tops $505.5 million, the size-of-person test disappears entirely. Both parties file regardless of size.

A reportable acquisition happens when you buy voting securities, non-corporate interests, or assets that, combined with what you already own, cross an HSR threshold. Voting securities include common and preferred stock with voting rights. Non-corporate interests cover partnership interests and LLC membership units with governance rights. Asset acquisitions are reportable when you get operational control over productive assets, not just contract rights. You have to add up all holdings of the same issuer when figuring out whether a new buy crosses a threshold, including shares acquired in separate transactions within the past year.

Filing Mechanics and Required Documentation for HSR Compliance

The HSR form is a detailed questionnaire about ultimate parent entities, organizational structure, revenue by business segment, overlapping activities, and prior acquisitions of the same issuer. You need to prepare ownership charts that trace control from the filing person up to the ultimate parent, identify all entities within the person, and show any entities being acquired. The form wants revenue data broken down by six-digit NAICS codes so agencies can spot product overlaps and vertical relationships. Start collecting documents and data at least 30 days before you plan to file. Preparing Item 4(c) and 4(d) documents, revenue schedules, and org charts often needs input from multiple business units, finance teams, and outside counsel.

Key items in typical HSR submissions:

1. Completed HSR form for both acquiring and acquired persons
2. Org charts showing all entities within each person and the acquisition structure
3. Revenue breakdowns for the most recent fiscal year, organized by six-digit NAICS code
4. Item 4(c) documents prepared by or for officers or directors to evaluate the deal (board decks, investment committee memos, management presentations)
5. Item 4(d) documents analyzing markets, competition, competitors, or market shares related to overlapping NAICS codes
6. Filing fee payment (wired or submitted electronically depending on deal value tier)

HSR filings go through the FTC’s PreMerger Notification Office portal electronically. Each party files separately. Both filings need to be substantially complete before the waiting period starts. Check that entity names, addresses, and ultimate parent info match across both filings to avoid processing delays. When state mini-HSR laws apply, deal teams coordinate federal and state timing. California requires submission within one business day of the federal filing. Some states want attachments immediately, others allow a seven-day window after a state AG asks for them. Accurate entity identification and early document collection cut down the risk of refiling or supplemental submissions that restart waiting periods.

Waiting Periods, Second Requests, and Early Termination Under HSR Rules

The standard waiting period is 30 calendar days from when the FTC or DOJ receives substantially complete filings from both parties. For cash tender offers and certain bankruptcy deals, it’s 15 calendar days. You can request early termination by checking a box on the HSR form. If granted, the agencies publish a notice and you can close right away. Early termination is discretionary. The agencies typically grant it only when they conclude after initial review that the deal raises no competitive concerns. It’s less common now than before. Many deals go through the full 30 days even when no second request comes.

If the reviewing agency spots potential competitive issues during the initial waiting period, it can issue a second request for more documents and information before the period expires. A second request is a detailed set of questions and document specs tailored to the transaction and markets involved. Once issued, the initial waiting period extends until 30 days after both parties substantially comply with the request (10 days for cash tender offers). Substantial compliance means certifying that all responsive documents have been produced and all answers are complete. Parties often negotiate the scope with agency staff to focus production on the most relevant materials and reduce burden. The extended period lets the agency conduct a full investigation, including depositions of company execs, interviews with customers and competitors, and economic analysis of competitive effects.

Timing strategies depend on deal structure and risk. Parties to non-controversial deals may file early to max out the chance of early termination or clearance before a planned closing date. Deals with known overlaps or vertical issues often involve pre-filing meetings with agency staff to discuss theories of harm and potential timing. Deals subject to multiple foreign filings may coordinate HSR timing with EU, UK, or Chinese merger control deadlines to avoid conflicting remedies or closing conditions.

Penalties, Enforcement Exposure, and Civil Liability Under Premerger Notification Rules

Federal civil penalties for HSR violations are adjusted yearly for inflation. They currently stand at up to $51,744 per day for each day you fail to file or close a deal during the waiting period. The FTC and DOJ decide when to seek penalties. They typically pursue them when parties intentionally avoid filing, close before clearance, or submit materially incomplete filings. Beyond daily penalties, agencies can unwind consummated transactions, forcing divestitures or operational separations that cost far more than the penalties. Courts have upheld penalty awards in cases where parties misunderstood thresholds, miscalculated holdings, or relied on incorrect legal advice. HSR compliance is a strict-liability obligation.

Common violations triggering penalties:

• Closing before the waiting period expires or before receiving early termination
• Failing to file when a deal exceeds thresholds due to incorrect aggregation or valuation
• Submitting incomplete filings that omit required documents, org charts, or revenue data
• Gun-jumping by integrating operations, sharing competitively sensitive information, or exercising control before clearance

State penalties vary by jurisdiction and are imposed separately from federal ones. California’s SB 25 authorizes civil penalties up to $25,000 per day for failing to submit required HSR materials or respond to requests for additional material within statutory deadlines, subject to a three-business-day cure period after written notice from the AG. Washington and Colorado, which enacted similar laws effective in 2025, impose maximum penalties of $10,000 per day. Rhode Island’s rule for medical-practice group deals imposes penalties up to $200 per day for missing the 60-day advance notice requirement and up to $100,000 for failing to notify by closing. These state penalties are independent of federal HSR penalties. You can face concurrent enforcement actions at both levels if you fail to satisfy overlapping federal and state notification obligations.

Emerging State Premerger Notification Rules and Their Interaction With Federal Requirements

A growing number of states have adopted “mini-HSR” statutes requiring parties who file federal HSR notifications to submit those filings to the state AG when specified state thresholds are met. These laws are modeled on the Uniform Antitrust Premerger Notification Act (UAPNA), which the Uniform Law Commission approved in July 2024. The UAPNA framework gives state enforcers early access to transaction information without creating duplicative review standards or additional waiting periods. Washington and Colorado enacted UAPNA-based laws in 2025. California followed in 2026. Other states, including New York, Hawaii, West Virginia, and D.C., are considering similar legislation. The trend reflects state AGs’ interest in monitoring large transactions with in-state effects, particularly in healthcare, technology, and labor markets where state enforcement priorities may diverge from federal focus.

California’s SB 25 was signed into law on February 10, 2026, and applies to HSR filings made on or after January 1, 2027. A filing party must submit a complete electronic copy of its federal HSR form to the California AG when either the party’s principal place of business is in California or the party (or an entity it controls) had annual net sales in California of the goods or services involved equal to at least 20 percent of the prevailing federal HSR filing threshold. With the current HSR threshold at $126.4 million, the 20 percent sales trigger equals $25.28 million in annual California net sales. Submissions must occur within one business day of the federal HSR filing. When the principal-place-of-business trigger applies, the party includes all “additional documentary material” (Item 4(c) and 4(d) documents) at submission. When the sales-based nexus triggers the obligation, the California DOJ may request additional material, and the party provides it within seven days. Filing fees are $1,000 for parties whose principal place of business is in California and $500 for parties meeting the sales-based trigger. California law prohibits the AG from making any component of the HSR form public. Materials are exempt from state public-records law. The AG may share materials with the FTC, DOJ, and other states that enacted UAPNA or equivalent statutes with comparable confidentiality protections. The AG must provide at least five business days’ advance notice to the submitting party before disclosing materials to another state. Civil penalties for noncompliance can reach $25,000 per day after a three-business-day cure period.

Washington’s law became effective for HSR filings made on or after July 27, 2025. Colorado’s took effect August 6, 2025. Both states apply the principal-place-of-business and 20-percent-sales triggers and impose maximum civil penalties of $10,000 per day. Washington also includes a healthcare-provider carve-in, requiring notification when a party is a healthcare provider or healthcare organization as defined by state law, regardless of sales or principal-place-of-business status. Rhode Island enacted a specialized rule for medical-practice groups on January 28, 2026, requiring written notice at least 60 days before any transaction that causes a “material change” to a medical-practice group. Material-change triggers include mergers, consolidations, affiliations, sales of substantially all assets, employment arrangements that place substantially all physicians under a hospital or related entity, formation of management service organizations, and equity investments of 10 percent or more resulting in change of control. The Rhode Island rule imposes no monetary transaction-value thresholds and applies penalties up to $200 per day for missing the 60-day notice and up to $100,000 for failing to notify by closing. The AG may seek injunctive relief to block proposed transactions.

From a compliance standpoint, federal and state filings interrelate but operate on separate tracks. State mini-HSR laws are non-suspensory. They don’t create state waiting periods or prevent you from closing once the federal HSR waiting period expires. State filings provide state AGs with the same confidential information the federal agencies receive, enabling earlier coordination between state and federal enforcers and allowing states to initiate independent investigations or participate in remedy negotiations. You need to identify at the outset of deal planning whether any party’s principal place of business or in-state sales meet state triggers, calculate state-specific sales figures, and prepare to submit complete electronic HSR copies (including documentary attachments when required) within one business day of the federal filing. Deal teams should engage antitrust counsel to map effective dates, monitor pending legislation, and ensure state-specific materials and fee payments are ready when the federal filing is made.

Exemptions, Exceptions, and Structuring Considerations Under Premerger Rules

The HSR rules include numerous exemptions that exclude certain deals from the filing requirement even when statutory thresholds are met. These exemptions are designed to avoid burdening transactions that pose minimal competitive risk or that involve routine corporate restructuring. Many state mini-HSR laws adopt the same federal definitions and exemptions to maintain alignment with the HSR framework and reduce duplicative analysis. Understanding exemptions is critical because misapplying one can result in failure to file and substantial penalties.

Common HSR exemptions:

• Intrafirm transfers: acquisitions of assets or voting securities solely among entities within the same person (controlled by the same ultimate parent)
• Certain acquisitions of real property: purchases of unimproved land, office buildings, and retail facilities not used in manufacturing or providing services
• Acquisitions solely for investment: purchases of voting securities with no intention to influence or control the issuer, limited to 10 percent or less
• Acquisitions of voting securities of issuers holding investment assets: purchases from issuers whose primary assets are cash, government securities, or other passive investments
• Certain acquisitions of foreign assets and voting securities: deals where U.S. sales attributable to the foreign assets or issuer don’t meet minimum thresholds
• Acquisitions in the ordinary course of business: purchases of current supplies, inventory, and similar items in normal operations

Aggregation rules require you to combine the value of all voting securities, non-corporate interests, or assets of the same issuer held by the acquiring person when determining whether a new acquisition crosses an HSR threshold. If you already hold $100 million of an issuer’s voting securities and acquire another $30 million, the new buy is reportable because total holdings ($130 million) exceed the $126.4 million threshold. HSR thresholds are set at $126.4 million, $252.8 million, $1.26 billion, and greater than $1.26 billion. Each crossing of a new threshold requires a new filing even if you previously filed for a lower threshold. Minority investments can be exempt if made solely for investment purposes with no board representation, shared governance, or operational involvement. Any indicia of control or influence may make the exemption unavailable. Parties considering restructuring deals (spin-offs, internal reorganizations, recapitalizations) should analyze whether the exemption for intrafirm transfers applies, recognizing that transfers between entities not controlled by the same ultimate parent aren’t exempt even when they occur within a commonly branded corporate family.

Market Definition, Competitive Effects, and Economic Analysis in Premerger Review

Agencies define relevant product and geographic markets to assess whether a deal is likely to substantially lessen competition. A product market includes all goods or services that consumers view as reasonable substitutes based on characteristics, uses, and prices. The agencies apply the hypothetical monopolist test, asking whether a hypothetical monopolist over a candidate group of products could profitably impose a small but significant price increase (typically 5 to 10 percent). If customers would switch to other products in sufficient numbers to make the price increase unprofitable, those substitute products are included in the market. A geographic market is defined by the area in which customers can reasonably turn for alternative sources and in which competitors operate. Geographic markets can be local (a city or metro area), regional (multi-state), national, or global, depending on shipping costs, transportation constraints, regulatory barriers, and customer behavior.

Market concentration is measured using the Herfindahl-Hirschman Index (HHI), which sums the squared market shares of all competitors in a defined market. An HHI below 1,500 indicates an unconcentrated market, 1,500 to 2,500 indicates moderate concentration, and above 2,500 indicates high concentration. The agencies also calculate the change in HHI (delta) resulting from the deal by doubling the product of the merging parties’ market shares. The 2023 Merger Guidelines indicate the agencies are likely to challenge deals in moderately or highly concentrated markets where the delta exceeds 100 to 200 points. The HHI is only a starting point. The agencies consider qualitative factors like entry barriers, buyer power, innovation effects, and the nature of competition.

Competitive effects theories fall into three categories: horizontal, vertical, and conglomerate. Horizontal mergers between direct competitors raise concerns about unilateral effects (the merged firm can raise prices or reduce output without coordinating with rivals) or coordinated effects (the merger makes collusion more likely by reducing the number of competitors or increasing transparency). Vertical mergers between firms at different stages of the supply chain can harm competition through foreclosure (the merged firm denies rivals access to key inputs or distribution channels) or by raising rivals’ costs. Unilateral effects analysis focuses on the extent to which the merging parties constrain each other’s pricing and the availability of close substitutes. State AGs gaining access to confidential HSR materials through mini-HSR laws may initiate early competitive assessments in coordination with the FTC or DOJ, or they may pursue independent state-law claims based on effects in local markets or on state-specific policy priorities like labor-market impacts or effects on small businesses.

Remedies, Divestitures, and Merger Conditions Related to Premerger Notification Rules

Remedies are typically required when the agencies conclude that a deal is likely to harm competition but that specific divestitures or conduct commitments can restore competitive conditions. The FTC and DOJ prefer structural remedies, requiring the parties to divest overlapping assets, business units, or customer relationships to a viable competitor. Structural remedies eliminate the competitive harm without requiring ongoing monitoring. Conduct remedies, like licensing agreements, supply commitments, or non-discrimination clauses, are disfavored because they’re harder to enforce and may not fully restore competition. But they’re sometimes accepted in vertical mergers or in markets where structural divestitures are impractical.

When the agencies identify competitive concerns during the initial 30-day waiting period or after issuing a second request, parties may propose a divestiture package to resolve the issues without litigation. A divestiture package typically includes the assets necessary to replicate the competitive constraint eliminated by the merger: manufacturing facilities, intellectual property, customer contracts, key employees, and supply agreements. The agencies require the divested assets be sold to a buyer approved by the agency and that the buyer have the incentive and ability to compete effectively. In some cases, the agencies require an upfront buyer (identified and approved before the merger closes) or a Crown Jewel provision (allowing the agency to designate additional assets for divestiture if the initial package can’t be sold within a specified period). Hold-separate orders require the merging parties to maintain the to-be-divested assets as independent, economically viable operations until the divestiture closes, preventing integration or commingling that would make it harder to sell the assets as a going concern. Consent decrees filed in federal court memorialize the agreed remedy and give the court jurisdiction to enforce compliance.

Negotiation strategies depend on the strength of the agencies’ case and the parties’ willingness to litigate. Parties with strong defenses or procompetitive justifications may resist remedies and proceed to litigation. Parties facing clear horizontal overlaps in concentrated markets often negotiate divestitures early to avoid protracted investigations or preliminary injunction proceedings. Timing impacts are significant. Remedy negotiations can extend investigations by several months. The need to identify, negotiate with, and obtain agency approval of a divestiture buyer adds complexity to deal planning. State participation in remedy negotiations, facilitated by mini-HSR filings that give state AGs access to confidential HSR materials, can lead to more coordination across federal and state agencies and occasionally to state-specific remedy requirements that reflect local market conditions or policy priorities.

Cross-Border and Multijurisdictional Notification Requirements

Large cross-border deals routinely trigger merger notification requirements in multiple jurisdictions, requiring coordination across U.S. federal HSR, state mini-HSR regimes, and foreign merger control systems. The EU, UK, China, Canada, Japan, Australia, Brazil, and dozens of other countries maintain their own notification thresholds, filing procedures, review timelines, and substantive standards. Each jurisdiction calculates thresholds differently. Some use worldwide turnover, others use local sales, and some combine both. Each applies different tests for reportability. Timing misalignment across jurisdictions can create significant risk. Clearance in one country doesn’t guarantee clearance in another. Conflicting remedies imposed by different agencies can make a deal impossible to complete as originally structured.

Coordinating multijurisdictional filings requires early mapping of which jurisdictions are triggered, calculating local-currency thresholds, preparing translated documents, and managing overlapping review periods. The EU’s merger regulation imposes a 25-working-day Phase I review (extendable to 35 working days) and a 90-working-day Phase II review (extendable to 110 working days) if the Commission identifies serious competitive concerns. The UK’s Competition and Markets Authority operates a two-phase system with a 40-working-day Phase I and a 24-week Phase II. China’s SAMR reviews deals within 30 days of accepting a complete filing for Phase I, with a 90-day Phase II if a detailed investigation is needed. Unlike the U.S., where the waiting period is suspensory, many foreign jurisdictions permit parties to close at their own risk before clearance. Doing so can result in significant penalties, unwinding orders, or criminal liability.

Common coordination challenges:

• Translating voluminous HSR Item 4(c) and 4(d) documents into local languages (German, Mandarin, Portuguese, Japanese) within tight deadlines
• Aligning timing so all filings are submitted within a narrow window, avoiding situations where one agency begins its review months before others
• Managing data privacy and confidentiality concerns when agencies request employee or customer data protected by GDPR or other data-protection laws
• Responding to inconsistent requests for information from multiple agencies investigating the same deal with different theories of harm
• Negotiating global remedies when one agency demands a divestiture and another clears the deal unconditionally, forcing parties to decide whether to implement the remedy worldwide or restructure the deal

Typical timelines in major jurisdictions vary but often overlap. EU Phase I reviews take 25 to 35 working days, UK Phase I reviews take 40 working days, and SAMR Phase I reviews take 30 days. All can extend into multi-month Phase II investigations. The U.S. HSR initial waiting period is 30 days, but second-request investigations routinely take six to twelve months. Canada’s Competition Bureau has a 30-day statutory waiting period but often negotiates timing agreements that extend the period. Deal teams should engage antitrust counsel in each major jurisdiction at the outset of deal planning, prepare a global filing calendar, and build timing cushions into merger agreements to account for potential second-phase reviews or remedy negotiations in one or more countries.

Final Words

In the action, this post explained the HSR Act: when federal filings are required, the size-of-transaction and size-of-person tests, the standard waiting period and second-request process, and the core HSR filing components.

States are adding “mini-HSR” obligations with their own penalties and timelines, but only the federal waiting period suspends closing.

Plan early, collect required documents, and coordinate federal, state, and cross-border filings. With clear roles and timelines, you can manage antitrust premerger notification rules and keep deals moving forward.

FAQ

Q: What is the purpose of the Hart‑Scott‑Rodino (HSR) Act and who must file?

A: The HSR Act requires parties to notify the FTC and DOJ before closing covered transactions when statutory thresholds are met, so agencies can review competitive effects; parties meeting size tests must file.

Q: What are the federal thresholds for HSR filings (size‑of‑transaction and size‑of‑person)?

A: The federal thresholds use a size‑of‑transaction test (adjusted annually, recently about $126 million) and a size‑of‑person test based on parties’ assets or sales; both tests determine filing obligations.

Q: What counts as a reportable transaction under HSR rules?

A: A reportable transaction includes acquisitions of voting securities, assets, or noncorporate interests that meet the size tests, covering stock purchases, asset deals, and steps that change control or competitive stakes.

Q: What documents are required in an HSR filing?

A: An HSR filing must include the completed form, transaction description, ownership charts, revenue breakdowns, relevant contracts and Item 4(c)/(d) documents, plus any required electronic copies for states.

Q: How long is the standard waiting period and how does early termination work?

A: The standard federal waiting period is 30 days (15 for cash tender offers); parties may request early termination, which, if granted, ends the wait and allows closing before the full period.

Q: What is a second request and what happens if one is issued?

A: A second request is an agency demand for extensive documents and information that extends review, triggers broad production obligations, and typically delays closing until the parties satisfy the request or settle.

Q: Do state “mini‑HSR” laws affect the federal waiting period?

A: State mini‑HSR laws require separate filings in some states, but they do not suspend or extend the federal waiting period; only the federal HSR wait controls transaction suspension.

Q: What penalties can apply for failing to file or late filings?

A: Penalties for failing or late filings include federal civil fines and state daily fines (up to $25,000/day in some states); enforcement varies and cure periods may apply in limited jurisdictions.

Q: Which exemptions commonly remove the need to file?

A: Common exemptions include intrafirm transfers, pure real‑property transactions, certain minority investments, treasury stock purchases, and specified financial or bankruptcy transfers—check specific statutory exclusions.

Q: How should deal teams prepare to meet HSR filing mechanics and logistics?

A: Deal teams should gather accurate entity IDs, ownership charts, revenue data, contracts, and documentary attachments, confirm electronic formats, and coordinate federal and any state submissions early.

Q: How do cross‑border deals affect HSR and other jurisdictions’ filings?

A: Cross‑border deals trigger U.S. HSR plus foreign notifications; coordinate timing, translations, data‑privacy limits, and potential inconsistent remedies to avoid filing conflicts and closing delays.

Q: When are remedies or divestitures typically required during review?

A: Remedies or divestitures are required when agencies identify likely anticompetitive effects; expect hold‑separate orders, negotiated divestiture packages, and timing implications tied to settlement negotiations.