SilverBox Corp IV filed a current report on August 5, 2026, disclosing that on August 4, 2026, the parties to its Business Combination Agreement with Parataxis Holdings LLC entered into a Second Amendment extending the Outside Date for completing the proposed business combination.

Key Highlights

  • Outside Date extended: The Second Amendment moves the deadline for completing the proposed business combination from August 6, 2026 to December 31, 2026.
  • Conditional further extension: If SBXD obtains an extension of its initial business combination deadline, the Outside Date may be further extended by written notice from either party, up to the shorter of the extension period or a mutually agreed period.
  • Original agreement date: The Business Combination Agreement was first entered into on August 6, 2025, among SBXD, Parataxis Holdings Inc. (the intended public company), two merger subsidiaries, Parataxis Holdings LLC, SilverBox Sponsor IV LLC, and Edward Chin.
  • Registration Statement on file: PubCo and the Company have filed a Registration Statement on S-4 (333-289994) with the Securities and Exchange Commission in connection with the proposed transactions.
  • Rule 425 filing: The current report was filed as a written communication pursuant to Rule 425 under the Securities Act.
  • Exchange and ticker: SilverBox Corp IV Class A ordinary shares trade on the New York Stock Exchange LLC under the symbol SBXD.

SilverBox Corp IV and Parataxis Holdings Amend Combination Timeline

SilverBox Corp IV (NYSE: SBXD), a Cayman Islands exempted company and special purpose acquisition company headquartered in Austin, Texas, disclosed that on August 4, 2026, it and the other parties to its Business Combination Agreement signed the Second Amendment to that agreement. According to the filing, the sole operational change made by the Second Amendment is to push the Outside Date, the contractual deadline by which the proposed business combination must be completed, from August 6, 2026 to December 31, 2026.

The filing identifies the intended transaction structure: upon completion of the proposed business combination, Parataxis Holdings Inc., a Delaware corporation referred to as PubCo, would become the publicly listed company. Two merger subsidiaries, PTX Merger Sub I Inc. and PTX Merger Sub II LLC, are wholly-owned subsidiaries of PubCo. SilverBox Sponsor IV LLC is identified as representative of the SPAC shareholders, and Edward Chin is identified as representative of the Company Holders. The filing states that the Second Amendment is attached as Exhibit 2.1, and that the description of the amendment "is qualified in its entirety by reference to the full text of the First Amendment and the terms of which are incorporated by reference herein."

The filing also notes that an S-4 Registration Statement (file number 333-289994), which includes a preliminary proxy statement of SBXD and a prospectus of PubCo, has been filed with the Securities and Exchange Commission in connection with the proposed transactions. The filing contains forward-looking statements and other information that, according to its own cautionary language, "does not purport to be all-inclusive" and is subject to the limitations described therein.

What Was Disclosed

SilverBox Corp IV reported a Second Amendment to its Business Combination Agreement with Parataxis Holdings LLC and related parties, extending the Outside Date from August 6, 2026 to December 31, 2026, with a provision for a possible further extension tied to any SPAC deadline extension SBXD may receive.