California Enacts Uniform Antitrust Premerger Notification Act

California has enacted the California Uniform Antitrust Premerger Notification Act (the Act), joining a growing number of states that require advance notice to state antitrust enforcers for certain transactions that already trigger federal Hart‑Scott‑Rodino (HSR) reporting obligations. Like the recently enacted Colorado and Washington laws, California’s statute is modeled on the Uniform Law Commission’s Uniform Antitrust Premerger Notification Act and is intended to provide state attorneys general with earlier visibility into transactions that may affect competition within their states. Importantly, the Act only applies to premerger notifications filed on or after 1 January 2027, so the Act will not have an immediate impact on covered transactions, but companies and their counsel should still take note and plan ahead.

The new California requirement does not replace or modify federal HSR filings, but instead, it imposes an additional, state‑level notice obligation for covered transactions with a California nexus. While the statute closely tracks the Colorado and Washington laws in structure, California has adopted several notable procedural, threshold, and enforcement differences. 

Transactions Covered

The Act applies to transactions that are subject to the federal HSR Act filing requirements and involve a person with a sufficient nexus to California.

A sufficient California nexus exists if a filing party has its principal place of business in California or has annual net sales in California of the goods or services involved in the transaction that are equal to or exceed 20% of the applicable federal HSR filing threshold.

By tying the California sales threshold directly to the federal HSR filing threshold, the statute does not establish a fixed dollar amount. Instead, the applicable California sales threshold will adjust automatically as the federal HSR thresholds are updated. For example, under the revised threshold of US$133.9 million effective 17 February 2026, this would mean local annual net sales of at least US$26.78 million.

Filing Requirements

For parties having their principal place of business in California, filers must submit a premerger notification filing to the California attorney general that includes a copy of the HSR Form filed with the Federal Trade Commission and Department of Justice, along with a complete electronic copy of any additional documentary material filed. Parties meeting the sales threshold, on the other hand, are required to submit a copy of their HSR Form, plus any additional documentary material that may be requested by the attorney general.

Timing

Unlike Colorado and Washington, which require filing contemporaneously with the HSR submission, the Act requires parties to submit the state filing within one business day of submitting their federal HSR filing.

Filing Fees

The Act authorizes the attorney general to impose a filing fee of US$1,000 for filers submitting because their principal place of business is in California or US$500 for filers submitting because they meet the California sales threshold or are submitting additional documentary materials in response to a request from the attorney general.

Confidentiality Protections

Information submitted to the California attorney general is confidential and exempt from public disclosure under state public records laws, subject to limited exceptions for disclosure to other antitrust enforcement agencies or pursuant to court order. These protections are intended to mirror the confidentiality treatment afforded to HSR filings at the federal level.

Enforcement and Penalties

Failure to comply with the California premerger notification requirement may result in civil penalties of up to US$25,000 per day, following written notice and a three‑business‑day opportunity to cure. 

Effective Date

The Act becomes effective on 1 January 2027, and it applies to transactions closing on or after that date that meet the statute’s criteria.

Practical Implications for Dealmakers

California’s enactment further expands the growing patchwork of state‑level premerger notification regimes, adding to similar requirements in Colorado, Washington, and other states considering comparable legislation. For transactions involving multistate operations, this development underscores the need for early, coordinated filing analysis.

What Companies Should Do Now

Companies and deal counsel should prepare to incorporate California‑specific sales‑threshold and nexus analysis into HSR compliance checklists; update internal transaction planning documents to reflect state‑level timing, fee, and penalty variations; and coordinate HSR and state filings in parallel to ensure timely and consistent submissions.