You need to file an issuer event report when an event affects the entire class of securities or related financial instruments in the same manner. This may also be a material change. [FN 6] If so, you will also need to file a material change report. However, not all material changes are issuer events. For example, while a company buy-back of shares might be considered a material change, it would not be an issuer event. Please see question 4.5.1 for how to report transactions under a normal course issuer bid.
FN 6 As defined in securities legislation.