Short answer: under Ontario’s Residential Tenancies Act, 2006, a tenant may only assign the tenancy or sublet the unit with the landlord’s consent; the Act deals with assignments in section 95 and sublets in section 97. When occupancy has been transferred to someone else in any other way, section 100 lets the landlord apply to the Landlord and Tenant Board to terminate the tenancy and evict both the tenant and the person now living there. The catch that decides these cases is timing: the Board’s own application materials are blunt that the s. 100 application must be filed no later than 60 days after the landlord discovers the unauthorized occupancy. Miss the window and the occupant can effectively become your tenant. That deadline shapes everything below.
The legal frame, in plain terms
Three situations get mixed together and should not be. An assignment means the tenant moves out permanently and hands the tenancy to someone new. A sublet means the tenant leaves for a period, someone else lives there, and the tenant intends to return. Both require your consent under the Act, and you cannot arbitrarily refuse it, which is precisely why the process matters: a tenant who wanted permission could have asked for it. The third situation, the one section 100 exists for, is the transfer that simply happened: the person paying you rent no longer lives there, and a stranger does. An unauthorized occupant is not automatically a tenant, but they can become one if you sit on your rights, so the question every landlord should be able to answer is not "am I annoyed" but "what date did I discover this, and what can I prove."
The 60-day clock changes how you gather evidence
Because the application window runs from discovery, two dates matter: when the transfer happened, and when you found out. Document your discovery immediately, the same day, in writing: what you saw or were told, by whom, with whatever artifact exists, a listing screenshot, a neighbour’s message, a name on a buzzer. That contemporaneous record does double duty. It anchors your 60-day window against any argument that you knew earlier and slept on it, and it starts the evidence file the Board will eventually read. From that moment, the job is compressing weeks of proof into days, which is exactly the situation where a licensed investigator earns their fee: a defined, short window of lawful documentation rather than months of drift.
What actually proves unauthorized occupancy
The Board decides on evidence of who genuinely lives in the unit, and that is a pattern question, the same pattern discipline we describe in our reference on LTB evidence. What carries weight: documented observation from lawful public vantage points across a handful of dates showing who comes and goes with keys, at residential hours, with groceries and laundry rather than a visitor’s rhythm; the original tenant’s absence over the same dates, or their presence somewhere else entirely; vehicles regularly present and their registered story; names appearing on the buzzer, mailbox or deliveries observable from common areas; and the digital layer, the tenant’s own advertising, a rental listing for your unit, a profile offering it furnished, captured with dates and preserved properly. Each item alone is deniable. Five of them across two weeks, timestamped and reported in a form built for a hearing, is how "I think someone else lives there" becomes an order.
Interviews matter too, done carefully. Neighbours often know exactly when the switch happened, and a professional statement taken early, with a name and date, outlasts a hallway recollection eight months later. What we do not do is pretext our way into the unit or into anyone’s accounts; evidence that starts with deception ends with a credibility problem, and the lawful version was available the whole time.
The short-term rental variant
The Airbnb version of this problem runs on the same statute but faster facts: rotating strangers with luggage, lockboxes appearing on railings, cleaning crews between "guests", and a listing that is discoverable with disciplined open-source work. Capture the listing itself the day you find it, calendar availability, photos matching your unit’s layout, host profile, because listings vanish the moment a tenant senses trouble. Municipal short-term-rental rules may add a second front, many Ontario municipalities require registration and restrict short-term rentals to principal residences, but the LTB case stands on the tenancy analysis above regardless of what the city does. The documentation package is the same: who is actually occupying, on what dates, under what arrangement, proven lawfully.
What not to do while you build the case
Do not change the locks, remove belongings, or lean on the occupant to leave; self-help eviction is unlawful in Ontario regardless of how clear the underlying breach is, and it converts your strong application into their strong one. Do not accept rent from the new occupant while you decide what to do, without advice, because payment patterns are how occupants argue themselves into tenancies. And do not burn your 60 days waiting for the situation to resolve itself. The clean sequence is the boring one: document discovery, gather the pattern evidence quickly and lawfully, get advice, file inside the window. Our landlord and tenant practice runs this file type on exactly that sequence, and our broader landlord guide covers the neighbouring problems that tend to travel with it.
Not legal advice
This article is general information about Ontario’s Residential Tenancies Act, not legal advice. Deadlines and remedies turn on exact facts and current law; confirm your specific situation with a paralegal or lawyer before filing, and never attempt a self-help eviction.
Frequently asked questions
Can my tenant sublet or Airbnb the unit without my permission?
No. Under Ontario’s Residential Tenancies Act, an assignment (s. 95) or sublet (s. 97) requires the landlord’s consent, though consent cannot be arbitrarily refused for these. Occupancy transferred any other way, including running the unit as a short-term rental for strangers, is the unauthorized situation s. 100 exists for, and it gives the landlord an application to terminate and evict, on a strict timeline.
How do I prove an illegal sublet or unauthorized occupant?
With pattern evidence of who genuinely lives there: lawful observation across multiple dates showing the occupant’s residential rhythm and the tenant’s absence, names on buzzers or deliveries visible from common areas, vehicles regularly present, neighbour statements taken early, and the tenant’s own listings or ads captured with dates before they disappear. Single observations are deniable; a documented pattern across two weeks rarely is.
How long do I have to file at the LTB about an unauthorized occupant?
The Board’s application materials for s. 100 are explicit: no later than 60 days after the landlord discovers the unauthorized occupancy. Miss it and the occupant’s position hardens, potentially into a deemed tenancy. Record the date and circumstances of your discovery in writing the day it happens, then move quickly on evidence.
Can I just change the locks on an unauthorized occupant?
No. Self-help eviction is unlawful in Ontario no matter how clear the tenant’s breach, and it exposes you to your own liability while destroying the credibility of your application. The lawful route is evidence, advice, and a s. 100 application filed inside the 60-day window.
Sources
- Ontario, Residential Tenancies Act, 2006, ss. 95 (assignment), 97 (subletting), 100 (unauthorized transfer of occupancy). Accessed August 7, 2026.
- Tribunals Ontario, Landlord and Tenant Board, Form A2 instructions (60-day filing requirement from discovery). Accessed August 7, 2026.
- Tribunals Ontario, Landlord and Tenant Board, Interpretation Guideline 21: Landlords, Tenants, Occupants and Residential Tenancies. Accessed August 7, 2026.