I think these are unnecessary questions, because if the tenancy agreement is silent, a guaranteed short-term rent (whether legal or contractual) can at any time have a rent increase, either by mutual agreement between the two parties or as part of the notice procedure under Section 13. The section 13 notice can still be used to increase the rent to a «market rent» and not be based on any index. Landlords often have to follow certain legal procedures when increasing rent. The two main requirements that landlords must fulfill are to notify the tenant in writing of the increase and to give this notification a number of days before the expiry of the tenancy agreement. Below is a typical letter on how to inform a monthly tenant that you will increase their rent. Assured Shorthold Tenancies allows the landlord to charge a higher rent after the initial fixed time limit, which is usually six or twelve months. The rent cannot be increased for the first fixed period. Clauses providing for very high increases are generally unseated. (for example, if the rent increase is not used to obtain a fair rent for the property, but to increase the rent to a level where the tenant might be forced to leave or artificially increase it above $100,000 to abstain from the guaranteed short-circuit rental agreement). A brake on tenancy could also be challenged by referring it to the rent assessment committee. If you are sure that the rental price should not be increased and find enough evidence of the real estate market to support you, stand up and defend your cause. You have the option to appeal to an external committee until the new rent comes into effect.
Not all leases contain a rental price verification clause. It is also worth mentioning that if there is a rent increase clause and the landlord uses S13, it will depend on whether the tenancy agreement is prescribed by law or periodically at the ala London District Properties Management Ltd v. Goolamy If a landlord decides to increase the rent but does not issue a clause 13, then the tenant is not obliged to pay the rent increase unless it is indicated in the rental agreement.