The benchmark is the open market rent, so the strongest support is evidence of what similar nearby properties actually let for (recent comparable lettings), alongside official rent-index context and a clear record of your reasoning.
A rent increase on a private assured tenancy in England now has a single route: a Section 13 notice. The Renters' Rights Act 2025 amended the Housing Act 1988 process and, from 1 May 2026, made it the only way to raise the rent.[1][2] The tenant can refer the figure to the First-tier Tribunal, so it has to stand on evidence, not instinct.[2]
What benchmark does a proposed rent have to meet?
The open market rent. Section 14 of the Housing Act 1988, as amended by the Renters' Rights Act 2025, defines it as the rent at which the property "might reasonably be expected to be let in the open market by a willing landlord".[3] Government guidance puts the same test plainly: "the price that would be achieved if the property was newly advertised to let".[2]
The benchmark has teeth. A tenant can refer the notice to the tribunal before the start date, which the tribunal must receive by then,[4] and the tribunal then determines the open market rent, never more than the figure on the notice.[5] Nor is the increase backdated: the old rent stays payable until the decision.[5][6] Evidence is what closes the gap between the rent you propose and the rent a tribunal would find.
What evidence carries the most weight?
Recent lettings of genuinely similar properties nearby. Official guidance tells tenants preparing a challenge to gather "evidence from similar nearby properties (similar size, features and location)" showing how much they were rented for.[4] Your notice will be tested against that standard, so build your case from it.
Achieved rents count for more than advertised ones. A listing shows what a landlord is asking, not what a tenancy was agreed at. Anchoring to the local market is already the norm: in the English Private Landlord Survey 2024, 79% of landlords who increased the rent at their most recent new letting said they set it in line with the local market rate.[7]
| Evidence | What it shows | Weight and watch-outs |
|---|---|---|
| Comparable lettings | What similar nearby homes actually let for | Closest to the statutory test; keep them recent and genuinely similar[4] |
| Your own completed reviews and lets | Achieved rents you can verify | Strong where local and fresh; comparables age quickly |
| ONS rent index (PIPR) | Average rent movement across the local authority | Official statistics, but a stock average, not a valuation of one property[8] |
| EPC and condition | The state of this specific property | The tribunal can consider condition when deciding the rent[6] |
Where does the ONS rent index fit in?
As context, in proportion. The ONS Price Index of Private Rents (PIPR) is the official monthly measure of private rent prices and inflation, published down to local-authority level in England.[8] In the 12 months to July 2026, average private rent in England rose 3.8% to £1,451 a month (ONS, August 2026 release).[9]
Treat it as context, not proof. PIPR tracks a local authority's whole rented stock, sitting tenants included, and an average cannot see the street, condition, or features of one property.[8] It shows the average drift since the last review, to sit alongside comparables, never instead of them. What is PIPR? explains the series, and the Free Rent Indexation Tool generates an indexed reference point from published ONS data.
What should the written record show?
Your reasoning, not just your numbers. A defensible file shows which comparables you relied on, the index context, property specifics such as the EPC and condition, and a short note on how they support the figure. If the Section 13 notice is later referred to the tribunal, that record is the case you produce.
This is the job the evidence pack does in MarketRent. Comparables come from your portfolio, third-party data, and saved portal listings, with PIPR indexation applied by default and the EPC matched to the property. Once you propose, the pack locks, so the record of what you relied on stays intact. You decide the figure. MarketRent brings the market context and comparable evidence together around it.
What if you have few comparables of your own?
A small or widely spread portfolio often cannot build a convincing range alone. Three ways to widen the base:
- Bring in third-party comparable data for streets and stock you do not manage.
- Save relevant portal listings into the evidence pack as market context.
- Turn on AutoSync, so completed reviews and new lets flow back in as comparables.
Quality still beats quantity. Two or three recent lettings that are genuinely similar in size, features, and location[4] are worth more than a dozen loose matches. For notice dates, Form 4A mechanics, and the challenge process, see the complete guide to rent reviews under the Renters' Rights Act.
This article is general information for letting agents in England, not legal advice.
Sources
- The Renters' Rights Act 2025 (Commencement No. 2 and Transitional and Saving Provisions) Regulations 2026 (SI 2026/421)
- MHCLG, Guide to the Renters' Rights Act
- Housing Act 1988, section 14 (determination of rent by tribunal), as amended
- GOV.UK, Apply for an open market rent determination
- Renters' Rights Act 2025, section 7 (challenging amount or increase of rent)
- Form 4A, landlord's notice proposing a new rent (GOV.UK, version 05.26)
- MHCLG, English Private Landlord Survey 2024 main report
- ONS, Price Index of Private Rents quality and methodology information (QMI)
- ONS, Private rent and house prices, UK (latest monthly bulletin; June 2026 edition, data to May 2026)