In mergers and acquisitions (M&A), an agreed closing date does not guarantee that a transaction can proceed on schedule. For deals subject to Hart-Scott-Rodino (HSR) requirements, regulatory review can delay completion even after the parties have finalized commercial terms.
The HSR filing process imposes mandatory waiting periods, while deeper antitrust investigations can extend the timeline by months. Understanding when notification is required, how regulators assess transactions, and what may delay clearance helps deal teams establish realistic schedules and manage contractual commitments.
What triggers an HSR filing requirement?
A Hart-Scott-Rodino (HSR) filing is required when a merger or acquisition meets federal premerger notification thresholds and no statutory exemption applies. The assessment begins with the transaction’s value and considers the parties’ financial size.
Under the Federal Trade Commission (FTC)’s 2026 rules, effective February 17, 2026, the following transaction-value thresholds apply:
- $133.9 million or less: No filing is required.
- Above $133.9 million through $535.5 million: Filing is required only if the size-of-person test is met. Generally, one party must have at least $267.8 million in annual net sales or total assets, and the other at least $26.8 million. Special rules apply to certain nonmanufacturing targets.
- Above $535.5 million: Filing required regardless of party size. The size-of-person test no longer applies.
Even when reporting thresholds are met, certain M&A transactions may qualify for exemptions under the HSR exemption rules (16 CFR Part 802). For example, an acquisition of less than 10% of a company’s voting securities may be exempt if made solely for investment purposes, without an intention to influence management.
Once a transaction is determined to be reportable, the acquiring party generally must pay an HSR filing fee. The amount depends on the transaction’s value, with the 2026 HSR filing fees divided into six tiers:
| Transaction value | Filing fee |
| Below $189.6 million | $35,000 |
| $189.6 million–under $586.9 million | $110,000 |
| $586.9 million–under $1.174 billion | $275,000 |
| $1.174 billion–under $2.347 billion | $440,000 |
| $2.347 billion–under $5.869 billion | $875,000 |
| $5.869 billion or more | $2,460,000 |
Separately, a filing triggers a standard 30-day waiting period, reduced to 15 days for cash tender offers and certain bankruptcy transactions.
These requirements affect both the transaction budget and closing schedule. Parties must account for filing costs and cannot complete the acquisition until the applicable waiting period expires or is terminated.
Historical transactions can provide useful context. Reviewing merger examples helps deal teams understand how regulatory challenges have affected transaction execution. However, previous outcomes cannot establish whether a current acquisition will receive clearance.
How the initial waiting period works
The HSR waiting period gives federal antitrust regulators time to assess a proposed transaction before the parties can close. It begins once the parties have properly submitted the required notifications and satisfied the applicable filing requirements.
The Federal Trade Commission (FTC) and the Department of Justice (DOJ) receive the filings, and one of the agencies handles the substantive review. The filings contain information about the parties’ businesses, transaction structure, and documents relevant to potential competitive effects.
Regulators then examine whether the acquisition could reduce competition, particularly where the parties compete in the same market. They may also request further information or contact customers and competitors to assess market conditions.
The initial review can produce three outcomes:
- Expiration: The waiting period ends, allowing the parties to complete the transaction, provided all other closing conditions are satisfied.
- Early termination: Regulators may end the waiting period before expiration.
- Second request: The reviewing agency requires additional information before completing its competitive assessment.
What happens when a second request is issued
A second request in the antitrust review requires the merging parties to provide additional documents and data, thereby extending the investigation. It typically arises when regulators identify potential competitive concerns that require further investigation.
These concerns may involve substantial market overlap or increased industry concentration. To investigate potential competitive effects, regulators may request internal communications, business records, and detailed economic data.
Responding may take months as the parties must collect, review, and produce responsive materials. The process also increases legal costs and demands substantial involvement from company personnel.
Once the parties substantially comply, a further 30-day waiting period generally applies, reduced to 10 days for qualifying cash tender offers and bankruptcy transactions. As a result, the merger clearance timeline can extend beyond statutory waiting periods, depending on the time required for document production and the scope of the investigation.
Building regulatory timing into the deal schedule
Deal teams should assess antitrust risk before signing the transaction agreement so the proposed closing date accounts for potential regulatory delays. Early consultation with the legal team helps assess the likelihood of an extended antitrust investigation and establish a realistic closing timeline.
Where competitive concerns could prolong regulatory review, deal teams should adjust the contractual commitments accordingly.
Key planning considerations include:
- Financing commitments: Ensure financing remains available throughout the anticipated review period, with provisions for potential extensions if closing is delayed.
- Contractual deadlines: Specify when either party may terminate the agreement if the deal has not closed by the agreed deadline.
- Stakeholder communications: Coordinate expected closing dates with the legal team before communicating timelines to employees, customers, and investors. Premature assurances may create uncertainty if regulatory review takes longer than anticipated.
How deal teams should prepare for regulatory approval in M&A
Effective regulatory preparation begins with evidence supporting the transaction’s competitive rationale. Deal teams should gather relevant business records before filing so the legal team can identify potential concerns and prepare consistent responses to regulators’ questions.
The preparation should focus on three areas:
- Market analysis: Identify relevant product and geographic markets, competitors, and potential overlaps between the merging businesses.
- Transaction rationale: Organize existing strategy documents explaining the acquisition’s commercial objectives and anticipated business benefits.
- Supporting evidence: Preserve relevant internal records and verify that market-share estimates and competitive assessments are supported by reliable data.
Regulatory scrutiny depends on the transaction’s specific competitive effects and market conditions. Preparing accurate documentation early can reduce delays caused by incomplete information.
Conclusion
HSR filing requirements introduce regulatory considerations that can affect transaction costs, closing dates, and contractual commitments. While some acquisitions complete the initial waiting period without extended investigation, others face additional document requests and prolonged agency scrutiny.
For dealmakers, the priority is to account for antitrust review in M&A transaction planning. Early analysis, realistic contractual deadlines, and reliable supporting documentation help teams manage uncertainty throughout the review process.
