In Ontario, Canada, tenants have the right to refuse entry to their rental unit for the purpose of showing the unit to potential buyers or renters. However, there are some exceptions to this right.

If the landlord has given the tenant proper notice of entry (at least 24 hours in advance), and the purpose of the entry is to show the unit to potential buyers or renters, the tenant cannot unreasonably refuse to allow entry.

If the tenant does refuse entry, the landlord may apply to the Landlord and Tenant Board for an order allowing them to enter the unit to show it to potential buyers or renters. The Board will consider the circumstances of the case and make a determination.

It's important to note that while tenants have the right to refuse entry for the purpose of showing the unit to potential buyers or renters, they are required to allow entry for other reasons, such as repairs or maintenance, as long as proper notice has been given.

Under Ontario's Residential Tenancies Act, landlords must give tenants at least 24 hours' notice in writing before entering the rental unit for any reason, including showing the unit to potential buyers or renters. The notice must include the reason for entry, the date and time of entry, and the name and phone number of the person who will be entering the unit.

If a tenant refuses entry, the landlord can try to negotiate with the tenant to find a mutually convenient time for the showing. If this is not possible, the landlord can apply to the Landlord and Tenant Board for an order allowing them to enter the unit to show it to potential buyers or renters. The Board will consider the reasons for the tenant's refusal and whether the entry is necessary and reasonable in the circumstances.

It's important for landlords to respect their tenants' right to privacy and quiet enjoyment of their rental unit, and to make every effort to minimize the disruption caused by showings. This includes giving tenants as much notice as possible, scheduling showings at reasonable times, and minimizing the number of showings to only those that are necessary.