Does my regulatory college care who I sell my practice to, or just that I notify them?

Both, generally, though the emphasis differs by college. Most Ontario regulatory colleges care very much about who ends up owning or controlling a professional practice, because many professions can only be practiced through licensed members, and a college's mandate is protecting the public, not just tracking paperwork. A sale to someone who isn't licensed to practice the profession, or a structure that gives an unlicensed party effective control while a licensed figurehead holds the shares, is the kind of thing colleges actively look for, not merely record.

Beyond that substantive concern, many colleges also expect to be notified of an ownership change so their records (and, where relevant, public registers) stay accurate, and so continuity of care or client service can be verified. Some colleges require notice before closing; others accept notice shortly after. Assuming a simple after-the-fact notification satisfies every college's expectations is a common mistake, since the consequences of getting the ownership question wrong can include jeopardizing the practice's certificate of authorization entirely.

Because these rules genuinely differ by profession, confirming your specific college's current requirements before structuring the deal is worth doing early, not once you're already committed to a buyer.