The Residential Tenancies Act always takes priority over a lease. This means a lease cannot take away any of a tenant’s rights under the law. For example, a lease may state the landlord only has to give two tenancy months’ notice to end a month-to-month periodic tenancy. This term in the lease is unenforceable because the Residential Tenancies Act states that landlords must give at least three months’ notice.
The landlord can waive their rights under the Residential Tenancies Act. This means that the landlord can agree to certain things that take away their rights. For example, if the lease says that a monthly periodic tenant only has to provide the landlord with a one week notice to move out, then the tenant would only have to provide a one week notice instead of one month. Only the landlord can waive their rights; the tenant cannot.
There are lots of topics that should be included in the lease that are not mentioned in the law at all. For example, the Residential Tenancies Act does not mention pets, but the lease should state whether or not pets are allowed.