The 24-hour notice, and what it must say
Section 27(1) of the Residential Tenancies Act lets a landlord enter "in accordance with written notice given to the tenant at least 24 hours before the time of entry" for a listed set of reasons: to carry out a repair or replacement or do work in the unit; to let a potential mortgagee or insurer view it; to let a qualified engineer or architect inspect it for a Condominium Act requirement; to inspect whether the unit is in a good state of repair and fit for habitation; or for any other reasonable reason for entry specified in the tenancy agreement.
Section 27(3) is the part landlords get wrong most often. The notice "shall specify the reason for entry, the day of entry and a time of entry between the hours of 8 a.m. and 8 p.m." All three. A text saying "the plumber will come by tomorrow" is not a notice of entry — it names neither a reason in the statutory sense nor a time, and it is not clear it is written notice of entry at all.
A separate subsection, 27(2), covers showings to a potential purchaser: same 24 hours' written notice, and a registered broker or salesperson can do it with the landlord's written authorization.
The two exceptions that need no notice
Section 26(1) is short: "A landlord may enter a rental unit at any time without written notice, (a) in cases of emergency; or (b) if the tenant consents to the entry at the time of entry."
Consent at the time of entry means exactly that. A clause in the lease saying the tenant agrees to entry in general is not consent at the time of entry, and it does not replace the notice. The safe reading is that consent has to be given at the door, for that visit.
"Emergency" is not defined by a list in the Act. In practice it is the situation where waiting 24 hours would cause harm or serious damage — a fire, a gas smell, a burst pipe or active flooding, no heat in winter, an electrical hazard. If you are debating whether it qualifies, it probably does not, and you should serve notice.
Two more entries with no written notice
Section 26(2) allows entry to clean, without written notice, if the tenancy agreement requires the landlord to clean the unit at regular intervals — at the times specified in the agreement, or if none are specified, between 8 a.m. and 8 p.m.
Section 26(3) allows entry to show the unit to prospective tenants with no written notice, but only once the tenancy is ending: the landlord and tenant have agreed to terminate or one has given notice of termination, the entry is between 8 a.m. and 8 p.m., and the landlord informs or makes a reasonable effort to inform the tenant before entering.
What this looks like in practice
Write the notice the moment you book the trade, not the morning of. Twenty-four hours is measured to the time of entry, so a notice delivered at 4 p.m. cannot support a 9 a.m. visit the next day.
Give a time, not a window that spans the day. "Between 8 a.m. and 8 p.m." is the outer legal boundary, not a booking. Adjudicators read a 12-hour window as a landlord refusing to commit.
Keep the notice and the delivery. The dispute is almost never about whether you meant to give notice; it is about whether you can show what was sent and when. Serve it in writing, keep a copy against the unit, and log the visit against the same record.
If the tenant lets the trade in at the door anyway, that is consent under section 26(1)(b) — but note it at the time. Consent you recorded is worth something later; consent you remembered is not.