State-Level Merger Control Grows: California Joins “Mini-HSR” Trend with Senate Bill 25

On February 10, 2026, California enacted Senate Bill 25 (“SB 25”), known as the California Uniform Antitrust Pre-Merger Notification Act. The new law takes effect on January 1, 2027, making California the third state—following Washington (effective July 27, 2025) and Colorado (effective August 6, 2025)—to implement a “mini-HSR” regime modeled after the Uniform Antitrust Pre-Merger Notification Act (“UAPNA”). The legislation reflects the growing state-level focus on merger oversight, and it signals California’s continuing intent to increase early pre-merger scrutiny and concurrent review of transactions with federal authorities.

California already has sector-specific pre-notification regimes. For example, the recently expanded Health Care Quality and Affordability Act requires certain entities involved with health care services to provide notice to the Office of Health Care Affordability for transactions impacting material assets or control. In the retail grocery and pharmacy sectors, parties must submit notice to the attorney general (“AG”) 180 days prior to closing. SB 25 establishes a broader, cross-industry notification requirement that will capture a significantly larger number of transactions.

Overview: Model Law and State Adoption

The Uniform Law Commission (“ULC”) introduced the model UAPNA in September 2024 to provide a consistent framework for state pre-merger notification requirements. In addition to adoption by California, Colorado, and Washington, similar legislation is now advancing in the District of Columbia, Hawaii, Indiana, and West Virginia, with Indiana’s legislation being the furthest along, drafted to go into effect on July 1, 2026. New York is considering a broader overhaul of its antitrust laws that may include a “mini-HSR” component as well.

Thresholds for Notification: Nexus, Sales, and the “Goods or Services Involved” Test

SB 25 mirrors the threshold requirements set by Washington, Colorado, and the UAPNA, requiring any party that files an HSR notification to also submit a copy to the California AG if either:

• The filing person’s principal place of business is in California; or
• The filing person (or any directly or indirectly controlled entity) made annual net sales in California of the goods or services involved in the transaction of at least 20% of the HSR filing threshold.

Defining the “goods or services involved in the transaction” is somewhat subjective. The ULC’s UAPNA commentary suggests that this is limited to sales in the same business category as the transaction’s assets, which may be easier to assess for the target than the acquirer. Whether the California AG will provide clarifying guidance is an open question, but in the interim, the ambiguity poses a challenge for companies with complex operations in assessing their filing obligations across states, and underscores why it is important to engage antitrust counsel to review filing obligations.

Filing Process, Documentation, and Timing

California’s requirement is non-suspensory: it does not impose a separate waiting period or require state approval to close. This aligns with the approach in Washington, Colorado, and the UAPNA. Although the law does not mandate AG approval of transactions or grant it the power to prohibit them, the AG can still use the information obtained through the law to issue civil investigative demands and file suit to block mergers under the existing antitrust laws.

In California, parties with a principal place of business in the state must file both the HSR form and all related documentary materials, while parties triggering notification solely under the net sales threshold need only file the HSR form unless the AG requests the documentary materials. This approach mirrors the UAPNA and Washington’s rules, whereas Colorado requires all filers who trigger notification to provide both the HSR form and related documentary materials. The law also allows reciprocal information sharing of the HSR form and documentary materials with other states that implement these notification requirements, subject to notice and confidentiality safeguards.

California is slightly more generous than other states in mandating that parties file with the state within one business day of the federal filing. By contrast, Washington, Colorado, and the UAPNA require “contemporaneous” submission.

Costs and Penalties

SB 25’s text specifies that the California AG “may impose” filing fees up to $1,000, depending on the factors triggering notice, and penalties of up to $25,000 per day for noncompliance. This discretionary language means parties should stay informed on further state guidance to determine whether these costs will ultimately be mandated and how the penalties may be enforced. By comparison, Washington and Colorado do not charge filing fees, and their penalties are capped at $10,000 per day, consistent with the UAPNA.

Conclusion

SB 25 significantly increases the notice and compliance obligations on parties to HSR-reportable transactions. Although the California statute tracks the federal HSR process rather than creating a separate system, companies must pay close attention to when a filing is required and what business documents must be included with the filing. Given California’s outsized economy, these requirements will capture a greater number of transactions than seen in Washington or Colorado. As the patchwork of state-level “mini-HSR” laws grows, early coordination with counsel will be essential to effective compliance.