How to defend a Section 13 rent increase at tribunal

Since 1st May 2026, Section 13 has been the only lawful way to increase the rent on an assured periodic tenancy in England. Rent review clauses and informal agreements with tenants no longer count, and every increase now has to be able to stand up if a tenant refers it to the First-tier Tribunal. Recent analysis of tribunal decisions since the Renters' Rights Act came into force makes uncomfortable reading for landlords who have not adjusted how they set rent: most challenged increases are being reduced, and the most common reason is weak evidence, not an unreasonable asking price. Here is what is going wrong and how to build a rent increase that holds up.

Why challenges are rising, and why they are landing badly

Before the Renters' Rights Act, most tenants simply accepted a rent increase or moved out, because contesting one meant navigating a process most people had never heard of. Under a Section 13 notice, referring the increase to the tribunal costs very little, the tenant keeps paying their current rent while the case is decided, and the tribunal cannot set a figure higher than what the landlord proposed. For a tenant, there is almost no downside to challenging. Unsurprisingly, the number of referrals to the First-tier Tribunal has climbed sharply since 1st May 2026.

One analysis of around 200 recent Section 13 decisions found that roughly three-quarters resulted in a rent lower than the landlord had proposed, with a typical reduction in the region of 7 to 8 percent. Nearly half of the written decisions pointed to a specific problem with the evidence a landlord had submitted, from comparables that did not genuinely match the property to no supporting evidence at all. That is not a story about tribunals being anti-landlord. It is a story about landlords bringing the wrong kind of evidence to a process that expects something more rigorous than an online listing.

What the tribunal is actually looking for

The single biggest misunderstanding is treating asking prices as proof of market rent. A tribunal gives very little weight to what similar properties are currently advertised for on the major portals. What carries weight is transaction-based evidence: rents that have actually been agreed and paid for genuinely comparable homes, together with enough detail about each one to explain why it is a fair comparison.

1. Achieved rent, not advertised rent: a comparable needs to be a rent that was actually agreed and let, ideally within the last few months, not a current listing that may never let at that price.
2. A genuine match: size, location, condition, furnishing status and the date the comparable was let all need to line up closely enough that the tribunal can see why it is relevant to your property.
3. Enough detail to justify adjustments: if your property is bigger, better condition or in a stronger location than a comparable, say so and explain what that is worth, rather than leaving the tribunal to guess.
4. Your own property's condition: evidence of recent improvements, such as a new kitchen or bathroom, supports a higher rent only if you can show what was done and when.

Building your evidence pack: step by step

The strongest position is one where the evidence exists before you serve the notice, not one assembled in a hurry after a tenant refers the case. A practical order to work through:

• Start the file when you decide on the figure, not after a challenge. Save the evidence you used to set the new rent at the time you set it, including dates, so you can show your reasoning was current.
• Pull genuinely comparable lets from local agents, not just portal listings. Ask agents what similar properties nearby have actually let for recently, since agreed rents carry far more weight than asking prices.
• Match each comparable against your property on size, condition, location and furnishing, and note where it differs so you can explain any adjustment you have made.
• Photograph your property's condition and keep receipts for any refurbishment or improvement that justifies charging above what a tired equivalent property would achieve.
• Serve the correct form with the right notice period, and diarise the deadline, since a defective notice can undo a well-evidenced case before it even reaches the tribunal.
• For a significant increase or a larger portfolio, consider a RICS-qualified surveyor's opinion on market rent. It costs money upfront but carries weight the tribunal cannot easily dismiss.

Our explainer on the Form 4A rent increase notice covers the paperwork itself in more detail if you want to check you are using the right form and giving the correct notice period before you serve.

The cost of getting it wrong

Losing a chunk of the increase is not the only cost. Tribunal cases are taking a median of around three months to resolve nationally, and considerably longer in London, with some cases running well beyond six months. Because a new rent only takes effect from the tribunal's decision, not backdated to when you served the notice, every month the case drags on is a month of rent you do not recover, whatever the eventual outcome. A landlord proposing a modest monthly increase who waits five months for a decision can lose most of a year's worth of the uplift before it even starts. Getting the evidence right the first time is not just about winning the figure, it is about avoiding months of delay altogether, since a well-evidenced notice is far less likely to be challenged in the first place.

Common mistakes worth avoiding

1. Relying on Rightmove or Zoopla listings as your only evidence, when tribunals want to see rents that were actually agreed and paid.
2. Picking comparables that do not really match, such as a different property type or a different part of town, without explaining the gap.
3. Assuming a round-number increase looks reasonable, rather than working back from what similar homes have genuinely let for.
4. Leaving the paperwork until a tenant pushes back, instead of building the file at the point you decide the new rent.
5. Forgetting the wider rules, such as the once-a-year limit on increases and the minimum notice period, which apply regardless of how strong your evidence is. Our guide to the Renters' Rights Act has the wider context if you want a refresher on how the rest of the Act affects your tenancies.

The bottom line

A Section 13 increase is no longer just a letter you send and hope sticks. It is a figure you may have to justify with real evidence in front of a tribunal, and the data so far shows most landlords who end up there are not bringing enough of it. Treat the evidence gathering as part of setting the rent, not an afterthought, and you put yourself in a far stronger position if a tenant does decide to challenge. Our

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