With a standard sales tax placed on legal cannabis, Canada would garner approximately $675 million ($507 million US) annually.
According to the report from the C.D. Howe Institute, “applying only federal and provincial sales tax (GST/HST, PST) results in over 90 percent of the marijuana market being regulated and $675 million in annual revenue”. The report notes that “Any increase in taxes beyond this level serves to increase the share of the black market and generates little additional revenue.”
The Institute breaks it down like this; “With the regulation of marijuana, the government has a choice to make: either legitimize the market or generate large revenues, not both.”