@killerbeedee
“I have a question about how to complete a Schedule 50 when there are no shareholders.”
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I don’t post tax advice here - but - This situation seems too dangerous not to comment on on a practice level…
I don’t know who your professional insurer is, but likely they will have a fatal heart attack if work such as tax filings are being done when the incorporation documents are not on file and have not been reviewed: memorandum, articles, central securities register, register of directors, and authorization appointing them. 
There is the danger that legally speaking, you are this fellow’s personal accountant, never having been legally engaged by authorized persons in the corporation’s legal documents for the corporation.
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Once you have attended to the basics of the corporations legal documents, I think you will find that your posted question will be a non-issue…
It seems obvious that this must have been a DIY incorp, and now they are going to get in even further out of their depth with doing holding company etc without a lawyer.
Also, Provincial law generally requires that they ALSO register in the Province, so that may well also be not compliant to lawfully carry on business in a Province.
They will be better off, and you will be a lot safer, if you tell them to ask their lawyer to send you the “permanent file” docs you need, and keep repeating that to them as often as necessary…
Stay safe out there!