The Evidence Gap: What 200 Rent Tribunal Decisions Reveal About Section 13 Rent Increases

Insights & Data Reports | 03 Aug 2026

Section 13 rent increases

When a tenant challenges a Section 13 rent increase, the outcome turns on evidence. LonRes analysed 200 market rent determinations published by the First-tier Tribunal (Property Chamber) to see what that evidence actually looks like. In almost half of the decisions that set out reasons, it was thin, one-sided or missing altogether.

47%

of reasoned decisions disclose an evidence problem

73%

of determinations came in below the rent the landlord proposed

96 days

median wait from application to decision (142 in London)

Source: LonRes analysis of the GOV.UK residential property tribunal decisions register, July 2026.

A note on the data

LonRes reviewed the GOV.UK register of residential property tribunal decisions on 29 July 2026. Of 1,325 rents decisions published since 1 January 2025, 830 were market rent determinations. We analysed a random sample of 200 of those, 169 of which set out the tribunal’s reasons. Percentages relate to the relevant subset, and the full methodology sits at the end of this article.

The new rules

Section 13 is now the only route to a rent increase

Since the Renters’ Rights Act came into force on 1 May 2026, rent review clauses in tenancy agreements no longer apply. A landlord who wants to increase the rent on a periodic tenancy must serve a Section 13 notice (Form 4A), giving at least two months’ notice, no more than once a year, at a level no higher than the open market rent.

The tenant, in turn, can refer that rent increase notice to the First-tier Tribunal (Property Chamber) for a market rent determination, using form MR1 and a £47 fee. Two features of the new framework change the calculation for landlords and their agents:

The tribunal cannot set a higher rent

HM Courts and Tribunals Service guidance is explicit that the determined rent will be lower than or the same as the figure in the landlord’s notice.

The new rent is never backdated

It takes effect from the rent period following the tribunal’s decision, so the difference between the proposed rent and the old rent is lost for every week the case waits.

For tenants, challenging costs little and postpones any increase. London’s letting agents saw this coming well before commencement. And because the official quarterly tribunal statistics will not capture the first full post-Act quarter until the autumn, the decision register is the earliest available evidence of how these cases actually run. So that is where we went.

The analysis

Nearly half of reasoned decisions show an evidence problem

We read the published text of all 200 sampled decisions and classified the language tribunals used about the evidence in front of them.

Of the 169 decisions with published reasons

47%

disclosed at least one evidence problem: an explicit shortage of comparable evidence, a party who provided nothing at all, or a panel falling back on its own knowledge of the market

39%

record the tribunal relying on its own knowledge and experience of the local market to reach a figure

21%

record that at least one party provided no evidence or representations at all

13%

use explicit gap language such as “no comparable evidence”, “limited market evidence” or “insufficient evidence”

Case in point

In a Romford determination, the panel noted “insufficient evidence” and reached its figure “using its own knowledge and experience of the rental market in Romford” (LON/00AR/MNR/2025/0668). In a North West case, no evidence was submitted by either party and the tribunal used its own knowledge to set the rent (MAN/30UF/MNR/2025/0984).

When a panel relies on its own expertise, the system is working as designed: tribunals include valuer members for precisely this reason. But for landlords, tenants and their agents it means the number is out of their hands. The party that does bring credible market evidence is the only one still influencing the outcome.

The outcomes

How can landlords and agents justify a rent increase at tribunal?

With evidence of achieved rents for genuinely comparable properties: what similar homes in the same market actually let for, when, and in what condition, with adjustments explained. Tribunals give little weight to asking prices. And where that evidence is missing, our analysis shows the determined rent usually lands below the figure on the notice.

The 108 sampled decisions stating both the proposed and the determined rent

73% were determined below the landlord’s proposed rent, with a median reduction of 7.5% among those cut.

18% confirmed the proposed rent.

9% were set above it, an outcome the previous rules allowed but the Renters’ Rights Act has removed.

The cautionary tale

With no evidence from either side, the panel in the North West case determined £900 against a proposed £1,100, an 18% reduction (MAN/30UF/MNR/2025/0984). In a Cambridgeshire case, a £1,500 notice became a £1,400 determination (CAM/12UB/MNR/2024/0616).

Under the new framework, that 9% upside has gone. A landlord who arrives at the tribunal with weak evidence now runs a one-way risk: the rent can only be confirmed or reduced.

The timeline

How long does a rent tribunal decision take?

Among sampled decisions that state the application date, the median wait from application to decision was 96 days, roughly 14 weeks. A quarter of cases took more than 24 weeks and the longest ran well past a year. In the London subset the median was 142 days, around 20 weeks.

Because the new rent is never backdated, the delay itself has a price. A £200 per month increase held up for five months is £1,000 the landlord never recovers, and in London a five-month wait is unremarkable. With challenge volumes widely expected to rise as the Act beds in, those waits are more likely to lengthen than shorten.

£1,000

never recovered when a £200 per month increase is held up for five months, because the new rent takes effect only from the tribunal’s decision.

The evidence

Asking rents are not evidence. Achieved rents are.

The Act has also made the most easily available “evidence” less reliable. Landlords and agents can no longer accept offers above the advertised rent, so asking rents on the portals are likely to be pitched high, widening the long-standing gap between asking and achieved rents. A tribunal panel knows the difference.

Asking rent: an aspiration

Achieved rent: the market, confirmed

achievedRentConfirmed

letDateRecorded

sizeAndConditionDetailed

adjustmentsExplained

A screenshot of an asking price is an aspiration; an achieved rent is the market, confirmed.

What carries weight is transaction-based comparable evidence: the achieved rent, the property’s size and condition, the letting date, and enough detail to justify adjustments. That is data agents themselves hold, collectively. LonRes members have been contributing lettings data since 2005, and can draw on more than 20 years of achieved lettings records across London.

The solution

The LonRes Rental Checker

The LonRes Rental Checker was built for exactly this moment. It turns achieved rents contributed by London’s letting agents into an independent, impartial market rent report for a specific property: evidence designed to support a Section 13 rent increase, respond to a tenant challenge, and stand scrutiny at the First-tier Tribunal.

“If you have to go to a tribunal, the data you get is exactly what you need.”

Mark Von Grundherr Benham & Reeves

“It is evidence, isn’t it? It’s a report. They can’t really argue with it.”

Charlotte Elkington Cluttons

The point is not only winning at tribunal. It is pricing the increase correctly in the first place, so that fewer cases get that far, and showing landlords that the figure on the Section 13 notice is grounded in what the market actually pays. Priced right and evidenced properly, an increase is much harder to argue with.

Rental Checker

Robust, impartial evidence for market rent determinations

Rental Checker reports are available to contributing LonRes members within the platform, ready for rent reviews, tenant challenges and the tribunal.

Access the Rental Checker → Book a free trial

FAQ

Frequently asked questions

How much can a landlord increase rent under the Renters’ Rights Act?

There is no fixed cap or formula. A landlord can propose any figure up to the open market rent, once a year, by serving a Section 13 notice with at least two months’ notice. If the tenant refers it to the First-tier Tribunal, the tribunal decides what the property would let for on the open market. In the LonRes analysis, 73% of determinations came in below the proposed figure.

How should letting agents evidence a Section 13 rent increase?

With comparable evidence based on achieved rents: recent lettings of similar properties, showing the rent actually agreed, the letting date and the property’s condition, with any adjustments explained. In 47% of reasoned tribunal decisions LonRes reviewed, the panel flagged missing or limited evidence or fell back on its own knowledge, so robust comparables are the clearest way to keep the outcome in your hands.

Where can letting agents find comparable evidence for a rent review?

An agent’s own lettings records are the starting point, but a single branch rarely holds enough directly comparable transactions. Shared, independent datasets fill the gap. The LonRes Rental Checker draws on achieved rents contributed by letting agents across London to produce an impartial market rent report for a specific property.

Can the tribunal set a rent higher than the landlord proposed?

No. Under the Renters’ Rights Act framework, the determined rent will be lower than or the same as the figure in the landlord’s notice. Under the previous rules the tribunal could go higher, and did so in 9% of the decisions LonRes analysed.

How long does a First-tier Tribunal rent determination take?

In the LonRes sample of published decisions, the median was 96 days from application to decision, and 142 days for London cases. Individual cases ranged from six weeks to well over a year.

Is the new rent backdated after a tribunal decision?

No. The new rent takes effect from the start of the rent period following the tribunal’s determination. Rent lost while the case was waiting cannot be recovered, which is why pricing and evidencing the increase correctly at the outset matters.

Method and sources

LonRes analysis of the GOV.UK register of residential property tribunal decisions, category “Rents”, decisions published from 1 January 2025, queried 29 July 2026. Of 1,325 decisions, 830 were market rent determinations (case references containing /MNR/, i.e. referrals under sections 13 and 14 of the Housing Act 1988); the remainder are mainly Rent Act 1977 fair rent registrations, which are out of scope. We drew a reproducible random sample of 200 market rent decisions and analysed the full published text of each. Evidence language was classified by systematic text patterns and spot-checked against the underlying decisions. Reasoning rates are reported against the 169 decisions with published reasons; outcome figures against the 108 decisions stating both proposed and determined rents; timelines against the 53 decisions stating the application date. “Own knowledge” wording can reflect routine practice as well as an evidence gap, which is why it is reported separately from explicit gap language. Case references cited: LON/00AR/MNR/2025/0668; MAN/30UF/MNR/2025/0984; CAM/12UB/MNR/2024/0616.

Legal framework: Renters’ Rights Act 2025 (rent provisions commenced 1 May 2026); HM Courts and Tribunals Service guidance on open market rent determinations (updated 1 July 2026). Agent quotations were gathered by LonRes in June 2026 and are reproduced with minor tidying for readability.