Can my spouse hold non-voting shares in my Ontario professional corporation?

Possibly, but it depends entirely on your profession's governing body, not on a single rule that applies to every professional corporation. Some regulators permit a spouse or other family member to hold non-voting shares in the corporation, generally as an economic interest for income-splitting or estate-planning purposes, while the licensed professional keeps the voting shares and control over the practice. Other governing bodies restrict all shares, voting and non-voting, to licensed members of the profession, with no family exception at all.

Because this varies by profession and by the specific rules your regulator has adopted, the right answer for a physician's professional corporation may not be the right answer for a lawyer's or an accountant's. Before adding a spouse as a shareholder, confirm the current position with your own governing body, and have the shareholding structure documented properly — including a shareholders' agreement addressing what happens to those shares on death, divorce, or disability. Getting this wrong can jeopardize the corporation's certificate of authorization, which is a bigger problem than any tax benefit it was meant to achieve.