Seventy-three per cent. That is the share of published First-tier Tribunal market rent determinations that came in below the landlord's proposed figure, according to LonRes's July 2026 analysis of 200 decisions drawn from the GOV.UK residential property tribunal register. Among the cases that were cut, the median reduction was 7.5%. On a Zone 2 two-bed going from £2,100 to £2,400, that is roughly £180 a month back in your account, every month, for as long as you stay.
The other number worth holding onto: 9% of decisions in that sample set the rent above what the landlord asked for. That outcome is no longer possible. Since 1 May 2026 the tribunal cannot determine a rent higher than the figure on the notice, which means the worst realistic result of a challenge is that the increase you were already facing is confirmed, later than it would otherwise have started.
What actually changed on 1 May 2026
Every assured tenancy in England is now periodic, Section 21 is gone, and the rent review clause buried in your old AST has no legal effect. GOV.UK's assured tenancy forms guidance confirms the single route: a Section 13 notice on the prescribed Form 4A, published for use on and after 1 May 2026. Form 4 is now social housing only.
Four rules follow from that, and letting agents are still getting them wrong:
- Once in any 12 months. The clock runs from the date the last increase took effect, not the date the last notice was served.
- Two months' minimum notice, doubled from the old one month for monthly tenancies.
- No informal increases. An email you replied to saying "fine", a new agreement at a higher figure, a CPI clause: none of these lawfully raise the rent on a periodic assured tenancy.
- The tribunal cannot go higher than the landlord's proposed rent, and a determined rent is the maximum lawful rent for that tenancy.
Check the notice before you argue about the money
Roughly half of the decisions in the LonRes sample that set out their reasoning showed evidence that was thin, one-sided or absent altogether. Before you get to evidence, though, check whether the notice works at all. The Renters' Rights Act expressly lets you challenge the validity of a notice proposing an increase, and a defective Form 4A has to be re-served from scratch, which buys you another two months at the old rent.
| What to check | Where it goes wrong | If it is wrong |
|---|---|---|
| The form itself | Old Form 4 used, or a solicitor's letter, or the agent's own template | Notice is very likely invalid; say so in writing before the effective date |
| Notice period | Fewer than two clear months between service and the proposed start date | Invalid; the landlord must start again |
| 12-month gap | New rent bites less than 12 months after the last increase took effect | Invalid, including where the last rise happened under the old rules |
| Start date | New rent starts mid-period rather than at the beginning of a rental period | Challenge it; the date must line up with your rent period |
| Service | Emailed when your agreement does not permit email service | Arguable; ask the agent to evidence how and when it was served |
Ask the agent one question in writing: "Please confirm the date this notice was served, the method of service, and the date the current rent took effect." Their answer, or their silence, is your first piece of evidence.
The deadline is the whole ballgame
Your application must reach the tribunal before the date the new rent is due to start. Miss that by a day and the increase simply takes effect, whatever the merits. There is no discretion to extend it, and no second bite until the landlord's next annual window.
The application fee is £47, set by the First-tier Tribunal (Property Chamber) Fees (Amendment) Order 2026 and confirmed in the April 2026 parliamentary debates, with no separate hearing fee and Help with Fees available if you cannot afford it. GOV.UK's form for referring a Section 13 increase has historically been Rents 1; agent-facing guidance from Goodlord refers to it now as MR1. Download whichever version is live on GOV.UK on the day you apply rather than a PDF someone linked to in a forum.
Two practical points. Tell your landlord in writing that you have applied, on the day you apply. And keep paying your existing rent by your normal method, on time, throughout. A clean payment record matters more than it used to now that open banking and rent payment apps make your history easy to produce as a single statement.
Build the bundle from achieved rents, not asking prices
Tribunal panels include RICS-qualified surveyor members who apply their own knowledge of the local market. They know that a portal listing is an aspiration. What lets is what counts.
Sources that carry weight:
- Achieved rents. HomeLet's index is built on rents actually agreed rather than asking prices, which is precisely why its own commentary makes a point of the distinction. Note that HomeLet's July 2026 index put Greater London annual rent growth at 6%, while the ONS Price Index of Private Rents, released 22 July 2026, put London's annual rent inflation at 2.2% in the 12 months to June 2026, the lowest of any English region. Where they disagree, lead with the ONS. It is the official series, and it measures the whole stock of rented homes rather than new lets only.
- Same street, same block, same layout. A flat two doors down at £1,950 beats a generic borough average. Screenshot the listing, note the date it was listed and the date it disappeared, and record any reduction along the way. A property that sat for nine weeks and dropped twice is evidence about the market, not just about that flat.
- Your own tenancy history. What you have paid, and for how long, and what was agreed when you signed.
- Defects that depress value. Damp, a broken extractor, single glazing, a boiler that has been "on order" since February, no working lift to the fourth floor. Photograph everything with dates and pair it with your repair emails. If the flat's EPC is weak, the energy retrofit rules give you a second line of argument about running costs and lettability.
What tribunals discount: portal asking prices with no evidence of a let, "similar" flats in a different price band a mile away, and vague claims about "the market". Six well-documented comparables within a ten-minute walk beat thirty screenshots.
One more thing worth saying plainly. Furnishings, white goods and improvements you paid for are disregarded when the panel assesses market rent. If you fitted the shelving or replaced the fridge, say so.
Timing is a discount in itself
Under the old regime a determination could be backdated to the notice date, so a six-month case could land as a lump sum. That is gone. Since 1 May 2026 the new rent takes effect from the start of the rent period following the tribunal's decision, and the tribunal can defer it by up to a further two months where paying immediately would cause undue hardship. You have to ask for that, with figures, either in your application or at the hearing.
The arithmetic follows. In the LonRes sample the median case took 96 days from application to decision, and 142 days for London cases, with individual cases ranging from six weeks to well over a year. If your London case runs to that 142-day median, that is nearly five months of paying the old rent on a rise you were told would start in two.
Say the notice proposes £2,300 from £2,100. Five months at the old figure is £1,000 you do not pay, before any reduction. If the panel then trims the increase to £2,215, that is the LonRes median 7.5% cut applied to a determined figure, and it compounds every month afterwards.
Be honest about the trade. Ministers were explicit during the fees debate that some tenants will apply purely for the delay, and the Act contains a reserve power letting the Secretary of State reintroduce backdating by regulation if the system is swamped. Applications since May have risen sharply. Assume the rules could tighten and do not build your finances around indefinite delay.
When challenging is the wrong move
Three situations where you should think twice.
The landlord has a Section 8 ground ready. Ground 1A, sale, and Ground 1, the landlord or family moving in, both require four months' notice and cannot be used in the first 12 months of the tenancy. If your landlord has already mentioned selling, a rent challenge does not stop a Ground 1A notice, and you could spend £47 and five months arguing about a rent you will not be paying by spring. Retaliatory eviction is unlawful, and a notice served purely because you challenged is vulnerable, but "vulnerable" means litigating it.
The proposed rent is genuinely at or below market. If your bundle is weak and the flat is objectively well priced, the panel confirms the figure. You have gained a few months of delay and spent hours on it.
You are in arrears. Ground 8 now requires three months' arrears and four weeks' notice. Sort the arrears first.
This week
Find the notice. Check the form number, the service date and the date your last increase took effect. Diarise the effective date and set a reminder ten days before it. Then email the agent: confirm you are considering a referral to the First-tier Tribunal, ask for the comparables the proposed rent is based on, and ask whether the landlord would agree a lower figure now rather than wait five months for a determination that cannot go above their asking price anyway.
A surprising number of agents, once they have read the LonRes numbers, will take the meeting.