In most private tenancies, a landlord must give at least 90 days’ written notice before a rent increase takes effect. The rent review generally cannot happen more than once in 12 months, and the notice must follow the required format and be sent to the RTB as well as the tenant. Rent-setting rules and limits may also apply, depending on the tenancy and property. If the notice appears invalid, check the RTB’s current guidance or consider using the RTB dispute resolution process; the outcome depends on the facts of the case.