SCHEDULE 13G/A 0001171843-24-006340 0001535845 XXXXXXXX LIVE 1 Class A ordinary shares, $0.0001 par value 03/31/2025 0002015947 SilverBox Corp IV G81354105 1250 S. Capital of Texas Highway Building 2, Suite 285 Austin TX 78746 Rule 13d-1(b) Healthcare of Ontario Pension Plan Trust Fund A6 1800000 1800000 1800000 N 8.8 FI In reference to Rows 5, 7 and 9 above, amount consists of 1,799,998 Class A ordinary shares, $0.0001 par value ("Class A Shares"), of SilverBox Corp IV, a blank check company formed under the laws of the Cayman Islands (the "Issuer"), and 2 Class A Shares held in the form of units, each consisting of one Class A Share and one-third of one redeemable warrant. Each whole warrant entitles the holder thereof to purchase one Class A Share at a price of $11.50 per share, subject to adjustment. In reference to Row 11 above, percentage ownership is based on 20,455,000 Class A Shares issued and outstanding as of March 13, 2025, as reported on the Issuer's annual report on Form 10-K for the fiscal year ended December 31, 2024, filed with the Securities and Exchange Commission on March 13, 2025. SilverBox Corp IV 1250 S. Capital of Texas Highway, Building 2, Suite 285, Austin, TX 78746 Healthcare of Ontario Pension Plan Trust Fund ("HOOPP") 1 York Street, Suite 1900, Toronto, Ontario, Canada, M5J 0B6 Ontario, Canada N FI A pension plan formed as a trust under the laws of Ontario, Canada and registered with the Financial Services Regulatory Authority of Ontario. See Item 9 on page 2. See Item 11 on page 2. See Item 5 on page 2. See Item 6 on page 2. See Item 7 on page 2. See Item 8 on page 2. Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. By signing below I certify that, to the best of my knowledge and belief, the regulatory scheme applicable to a pension plan formed as a trust under the laws of Ontario, Canada and registered with the Financial Services Regulatory Authority of Ontario is substantially comparable to the regulatory scheme applicable to the functionally equivalent U.S. institution(s). I also undertake to furnish to the Securities and Exchange Commission staff, upon request, information that would otherwise be disclosed in a Schedule 13D. Healthcare of Ontario Pension Plan Trust Fund /s/ Abas Kanu 05/14/2025