California has officially joined the growing cohort of states imposing mandatory premerger notification requirements, a development that significantly alters the compliance checklist for M&A transactions with a nexus to the nation’s largest state economy. Governor Gavin Newsom signed Senate Bill 25 (SB 25), the California Uniform Antitrust Premerger Notification Act (the Act), into law on February 10, 2026. This move solidifies a trend of state attorneys general seeking earlier visibility into major transactions that might impact local competition. For investment professionals and corporate development executives, this mandates a new layer of antitrust risk management ahead of closing.
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Effective January 1, 2027, the Act requires certain parties who already file under the federal Hart-Scott-Rodino (HSR) Act to submit a copy of that filing to the California Attorney General (AG) within one business day of the federal submission. Importantly, California is the third state to adopt such a regime modeled on the Uniform Law Commission’s Uniform Antitrust Premerger Notification Act, following similar laws enacted in Colorado and Washington.
Defining the California Nexus for HSR Filers
The California requirement is explicitly tethered to the federal HSR framework, avoiding the creation of an independent, parallel review regime with its own novel thresholds or forms. The obligation is triggered for any person making an HSR filing if they meet one of two specific California nexus tests:
- The filing party has its **principal place of business in California**.
- The filing party, or an entity it controls, had annual net sales in California of the goods or services involved in the transaction that equal or exceed **20% of the operative federal HSR size-of-transaction threshold**.
Because the sales threshold is tied directly to the annually adjusted HSR threshold—which stood at a transaction size minimum of $133.9 million as of mid-February 2026—dealmakers must incorporate state-level sales data analysis early in their M&A compliance planning. Counsel must now integrate this nexus analysis directly alongside their federal HSR compliance checklists.
Key Procedural Differences and Compliance Costs
While the Act mirrors its counterparts in structure, California has established distinct financial and procedural implications for non-compliance:
| Feature | California SB 25 | Comparison Note |
|---|---|---|
| Effective Date | January 1, 2027 | Gives deal teams time to prepare for the new compliance step. |
| Waiting Period | Non-suspensory | Closing is not automatically halted pending state review. |
| Filing Fee | Up to $1,000 | A departure from Colorado and Washington, which do not charge fees under their versions of the Uniform Act. |
| Civil Penalty (Non-Compliance) | Up to $25,000 per day | Significantly higher than the $10,000 per day cap in Washington and Colorado. |
| Cure Period | Three business days after written notice | Mitigates risk of immediate, substantial penalties for inadvertent errors. |
The potential for steep daily fines underscores the need for robust internal transaction planning to ensure adherence to the one-business-day deadline following the federal filing.
Strategic Implications: Scrutiny and Information Sharing
The primary motivation for SB 25 is providing the California AG with earlier access to transaction details, facilitating coordination with federal antitrust enforcers like the FTC and DOJ. While the law is non-suspensory—meaning a deal can technically close without state approval—the early notification increases the risk profile for transactions impacting California markets.
The new regime allows the AG to initiate civil investigative demands or file suit under existing antitrust statutes based on information received sooner in the deal lifecycle. Furthermore, the Act includes reciprocity provisions, allowing the California AG to share the submitted information with other states that have adopted the Uniform Act or a substantively equivalent statute (like Washington and Colorado), provided confidentiality standards are met.
For private equity firms and strategic acquirers targeting companies with significant California operations, this development signals several actionable items:
- Early Nexus Assessment: Transaction due diligence must now include a detailed calculation of California sales relative to the HSR threshold as soon as the deal structure is formalized.
- Gun-Jumping Vigilance: Heightened state-level review emphasizes the criticality of avoiding “gun-jumping” violations—improper information exchange during negotiations—as more regulators will be reviewing the submitted documents.
- Regulatory Timeline Expansion: While the *closing* is not suspended, the administrative burden and the potential for subsequent state investigation mean deal timelines must account for this concurrent state-level compliance step.
Given California’s immense economic footprint, legal experts suggest its new premerger notification mandate will have a more substantial impact than similar laws in other states. Investment bankers advising on cross-border M&A trends and technology sector transactions must proactively budget time and resources to satisfy these state-level disclosure mandates beginning in 2027.
