Since the Renters' Rights Act's main provisions commenced on 1 May 2026, there's exactly one lawful way to increase rent on an assured periodic tenancy: a Section 13 notice. Rent review clauses written into tenancy agreements, informal agreements with a tenant, anything else, none of it works anymore, and any clause attempting to allow it has no legal effect.
The notice period has doubled. Before the Act, a Section 13 notice needed one month's notice. It's now two months, for any notice served from 1 May 2026 onward. The notice also has to be served on the correct prescribed form, Form 4A, a homebrew letter with all the right information still isn't valid if it isn't on the correct form.
You can only increase rent once every 12 months, and there's now a new protection on top of that: rent cannot be increased at all within the first 12 months of a tenancy. The 12-month gap between increases is calculated from when the rent was last actually set or changed, not from the date of the last notice you served, a common mistake that can invalidate a notice served too early.
The Tribunal process changed in landlords' favour, in one specific way. A tenant who thinks a proposed increase is above market rate can refer it to the First-tier Tribunal (Property Chamber) at any point before the effective date. Under the old rules, the Tribunal could set the rent higher than what the landlord had proposed, occasionally happened, and it made some landlords nervous about testing the market properly. Under the current rules, the Tribunal is capped at the landlord's proposed figure, it can confirm it, or reduce it, but it can never increase it beyond what you asked for. That removes a real historic risk from pricing an increase confidently.
There's no backdating either way. If a case goes to Tribunal, the new rent only takes effect from the Tribunal's determination date forward, not retrospectively. Any gap between when you proposed the increase and when the Tribunal ruled isn't recoverable, which is exactly why getting the figure right and well-evidenced the first time matters more than it used to.
What this means practically. Section 13 is now unforgiving of shortcuts. The right form, the right notice period, the right gap since the rent was last changed, and a figure you can actually justify against comparable local rents, all four need to line up, or the notice risks being invalid before it even reaches a tenant's decision about whether to challenge it.
For the wider picture of what changed on 1 May 2026, including the end of Section 21, see our earlier piece on what the Act means for landlords day to day.