A landlord must serve a valid rent review notice, stating the new rent, the date it takes effect, and the information required by current tenancy rules. Depending on the tenancy and whether rent-control limits apply, this may include the calculation used and comparable rents from the RTB Rent Register. The landlord should retain documents such as the previous rent, relevant calculations and comparable-property evidence if the increase is challenged. If you believe the notice or evidence is inadequate, you can ask the RTB to assess the dispute; a solicitor can advise on the facts of your tenancy.