National Policy on Disclosure Standardslink below
It is fundamental that everyone investing in securities have equal access to information that may affect their investment decisions. The Canadian Securities Administrators ("the CSA" or "We") are concerned about the selective disclosure of material corporate information by companies to analysts, institutional investors, investment dealers and other market professionals. Selective disclosure occurs when a company discloses material nonpublic information to one or more individuals or companies and not broadly to the investing public. Selective disclosure can create opportunities for insider trading and also undermines retail investors' confidence in the marketplace as a level playing field. The definition of a "material fact" includes a two part materiality test. A fact is material when it (i) significantly affects the market price or value of a security; or (ii) would reasonably be expected to have a significant effect on the market price or value of a security.
2.1 Timely Disclosure
Companies are required by law to immediately disclose a "material change" in their business. For changes that a company initiates, the change occurs once the decision has been made to implement it. This may happen even before a company's directors approve it, if the company thinks it is probable they will do so. A company discloses a material change by issuing and filing a press release describing the change. A company must also file a material change report as soon as practicable, and no later than 10 days after the change occurs.
https://www.osc.ca/en/securities-law/instruments-rules-policies/5/51-201/national-policy-np-51-201-disclosure-standards