Refer to this ProTaxCommunity.com post thread.
During the past 20+ years I have revisited this topic several time. CRA does not seem to have a current definitive administrative policy on how to complete T2 S50. Their aim is to record the top 10 controlling shareholders for compliance, audit, and recovery of taxes owing purposes. This seems to limit shareholders to voting shares only since non-voting shareholder have no control. No clarification on how to handle multiple classes. Recommendation to track shares by type and class with registers and continuity logs.
In 2020 CPA Canada advised members of a T2 Schedule 50 project. This project attempted to use the Schedule 50 to track down controlling shareholders. I am unaware of any externally shared results of this project. In conversing with some senior CRA Businees Enquiries agents it seems that this project has taken a lower priority due to Covid-19 and several other ongoing projects.
Scroll down to Schedule 50
https://www.cpacanada.ca/business-and-accounting-resources/taxation/blog/2020/september/cews-international-tax-cra-updates
Maintaining corporate records
CRA
KATA
Ownr
Share Registers
…Certificates
…Share continuity by type and class, date, # of shares, value, shareholder
…Shareholder info continuity by name and tax#
…Treasury register by share type and class, date, $ in / $out
Minutes
… Shareholders
… Directors
Shareholder Agreements
… Spells out buyouts, valuation, etc.
For small, private corporations it is the rare few who maintain their corporate record books fully and up to date.