The one-per-year rule
Under the Renters' Rights Act 2026, a landlord may not increase the rent more than once in any 12-month period. This applies whether you are in a fixed-term tenancy or a periodic tenancy. If your landlord has already raised your rent within the last 12 months, any further increase during that period is unenforceable.
The 12-month period is measured from the date the last increase took effect, not from the start of your tenancy or the date notice was served. Keep a record of when any previous increases came into force.
Form 4 and the two-month notice requirement
Any proposed rent increase must be given in writing using the prescribed Form 4. An increase notified by text, email, or a letter that does not use the prescribed form is not valid and cannot be enforced.
The notice must be served at least two months before the new rent is due to take effect. If your landlord serves Form 4 on 1 June proposing an increase from 1 August, that is exactly two months and is valid. If they serve it on 10 June proposing an increase from 1 August, the notice period is insufficient — the increase cannot take effect until the correct two months have elapsed.
Is there a maximum percentage increase?
The Act does not set a maximum percentage by which rent can be increased. There is no 'rent cap' in the sense of a percentage limit. The legal test for whether a proposed rent increase is valid is whether it is at or below the open market rent for the property.
This means that in theory, if the market rent for your property has risen substantially, your landlord could propose a large increase and it would be technically lawful — provided it does not exceed what a new tenant would pay for the same property on the open market. However, you have the right to challenge any proposed increase at the First-Tier Tribunal.
How to challenge a rent increase
If you receive a Form 4 and believe the proposed increase is above market rate, you can apply to the First-Tier Tribunal (Property Chamber) before the increase takes effect. The application is free. The Tribunal will assess the open market rent for your property and, if your landlord's figure is higher, reduce it to market rate.
You must apply before the date the new rent is due to take effect. If you do not apply in time and simply pay the higher rent, you may be taken to have accepted it. Use our free rent checker tool to assess whether your proposed increase is likely to be within market rate before deciding whether to apply to the Tribunal.
During the Tribunal process, you should continue paying your current rent. Do not withhold rent as this could constitute arrears and give your landlord grounds to seek possession.
What if my landlord increases rent without using Form 4?
An increase notified without using Form 4, or with less than two months' notice, is unenforceable. You are not legally obliged to pay the higher amount. If your landlord tries to use the unpaid difference as a basis for a rent arrears claim, you should be able to challenge it on the grounds that the increase was invalid.
If your landlord persists in demanding an invalid increase, you can complain to the PRS Ombudsman or seek advice from Citizens Advice or Shelter.