ONEX CORPORATION — Proxy Solicitation & Information Statement 2024

Feb 23, 2024

161 Bay Street Toronto, Canada M5J 2S1 Phone: (416) 362-7711 www.onex.com

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February 22, 2024

Nova Scotia Securities Commission Alberta Securities Commission Manitoba Securities Commission Ontario Securities Commission Securities Office, Prince Edward Island Superintendent of Securities, NWT Superintendent of Securities, Nunavut

Securities Commission of Newfoundland and Labrador Saskatchewan Financial Services Commission New Brunswick Securities Commission British Columbia Securities Commission Autorité des marchés financiers Superintendent of Securities, Yukon

Re: Onex Corporation (the "Corporation")

We wish to advise you of the following information in connection with the Corporation's Annual Meeting of Shareholders:

Date of meeting: May 9, 2024 Record date for notice: March 25, 2024 Record date for voting: March 25, 2024 Beneficial ownership determination date: March 25, 2024 Securities entitled to notice: Subordinate Voting Shares Multiple Voting Shares Securities entitled to vote: Subordinate Voting Shares Multiple Voting Shares CUSIP / ISIN: 68272K103 / CA68272K1030 Issuer mailing directly to non-objecting beneficial owners: No Issuer will pay for objecting beneficial owner material distribution: Yes Issuer using notice-and-access for registered holders: Yes Issuer using notice-and-access for beneficial owners: Yes Notice-and-access stratification criteria: N/A

The Corporation intends to use the notice-and-access mechanism to send proxy-related materials to all registered holders and beneficial owners.

Yours very truly,

/s/ Colin Sam

Colin Sam

General Counsel & Secretary