Mississauga requires second units to meet the Ontario Building Code, Ontario Fire Code and City zoning bylaw, and to be registered with the City. For an existing unit, the registration step depends on the building-permit record. A listing in the City’s registry and an inspector-signed permit are related records, but they answer different questions.
Find or complete the building-permit record
To register an existing second unit, the City asks for proof of ownership, the second-unit building permit signed off by all concerned City inspectors, and the completed registration form. If a permit was never obtained, the owner must apply for a building permit before completing registration. If the owner does not have a permit copy, Mississauga directs them to call 311 for help locating it.
The registration itself has no fee according to the City’s current page. That does not mean legalization is cost-free: building permit, fire inspection, professional design and renovation charges may apply. The City says registered units are added to its Second Units Registry List, which is updated in the second week of each month. Check the current list and the property’s permit file rather than relying on an old printout or verbal description.
Match the registry entry to current conditions
A registry entry should not be treated as a complete inspection of the property today or proof that later changes were permitted. Compare the address, approved plans, unit layout, permit sign-offs and current conditions. Confirm any open corrections and applicable fire, zoning and building requirements with the City.
Use Mississauga’s second-unit registration guidance and current registry list for the latest requirements. For a unit with no permit, ask the City which application and inspections are required before registration. For the general records method, see how to check an existing ADU’s legal status.