Start with the part that is not a grey area
Whether a particular defect must be volunteered in Alberta is a legal question that turns on the facts, and it belongs with a real estate lawyer — not with a REALTOR® and certainly not with an internet answer.
What is not a grey area is representation. A suite cannot be advertised as legal, permitted or registered unless it actually is. Describing an unpermitted suite as a legal suite is a misrepresentation that can follow you long after possession, and it is the single most common way sellers turn a manageable situation into a serious one.
Assume the buyer will find out
- The City's secondary suite registry is public, and buyers check it.
- A home inspector notices egress windows, furnace arrangements and fire separation immediately.
- The buyer's lender or insurer may ask directly, and their answer can end the deal at the worst moment.
- Neighbours talk. So do past tenants and the previous listing history.
A discovered surprise costs far more than a disclosed one. Buyers price a known issue; they walk away from a hidden one.
How to sell the house anyway
Plenty of Calgary homes with unpermitted basement development sell perfectly well. The ones that go smoothly do three things: they describe the space accurately — developed lower level with a kitchenette, not a legal suite — they price it as what it is rather than as income property, and they have the answers ready before the first showing.
It is also worth finding out what compliance would actually require before you list. Occasionally it is achievable and changes the whole conversation; more often it is not, and knowing that lets you price with confidence instead of hope. See also selling as-is.