Company: SBXD
Filing Date: 2025-08-07
Form Type: 8-K/A
Source: 0001104659-25-075273
Chunk: 1

Company: SilverBox Corp IV
Filing Date: 2025-08-07
Form: 8-K/A
Chunk 1
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| Redeemable Warrants included as part of the units, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 |     | SBXD.WS   |     | New York Stock Exchange LLC |

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

This Amendment amends the Current Report on Form
8-K of SilverBox Corp IV, filed with the Securities and Exchange Commission (the “SEC”) on August 6, 2025 (the “Initial Current Report”) solely to include the SEPA and SEPA Registration Rights Agreement (as defined below) as Exhibits 10.7 and
10.8, respectively, and to file a corrected version of the Business Combination Agreement (as defined below) as Exhibit 2.1 with updated
references to the SEPA and SEPA Registration Rights Agreement.

Item 1.01 Entry into a Material Definitive Agreement.

Business Combination Agreement

As previously disclosed in the Initial Current Report, on August 6, 2025 (the “Execution Date”), SilverBox Corp IV, a Cayman Islands exempted company (“SPAC”), Parataxis Holdings Inc., a Delaware
corporation (“Pubco”), PTX Merger Sub I Inc., a Delaware corporation and a wholly-owned subsidiary of Pubco (“SPAC Merger Sub”), PTX Merger Sub II LLC, a Delaware limited liability company and a wholly-owned subsidiary of Pubco (“Company Merger Sub”), Parataxis Holdings LLC, a Delaware limited liability company (the “Company”), SilverBox Sponsor
IV LLC, a Delaware limited liability company (the “Sponsor”), solely for certain limited purposes as representative
of the SPAC Shareholders (the “SPAC Representative”), and Edward Chin, solely for certain limited purposes as representative
of the Company Holders (the “Seller Representative”), entered into a business combination agreement (the “Business Combination Agreement” and, the transactions contemplated by the Business Combination Agreement,