Section 13 Rent Rises: How London Tenants Win at Tribunal

Two things are true of a Section 13 challenge since 1 May 2026, and most tenants know neither. The First-tier Tribunal cannot set your rent higher than the figure your landlord asked for. And while your case is pending, you carry on paying the old rent, with nothing backdated when the decision lands. The downside risk that used to make challenging a rent rise a gamble has been engineered out. What is left is a process where the worst realistic outcome is the number you were already being told to pay.

That is the argument for reading your notice properly rather than replying "fine" to the agent's email.

What actually changed on 1 May 2026

The Renters' Rights Act 2025 came into force on 1 May 2026. Rent review clauses in tenancy agreements are void. Informal "we're putting it up to £2,300 from September" emails have no legal effect. On an assured periodic tenancy in England, a Section 13 notice on the prescribed Form 4A is now the only lawful route to a higher rent, and it can be used once every 12 months.

The mechanics tenants care about:

• Two months' notice minimum. The old one-month period for monthly tenancies is gone.
• The tribunal cannot go up. The Act inserted new provisions into the Housing Act 1988 capping the determination at the open market rent or the landlord's proposed rent, whichever is lower. Farrer & Co's analysis of the rent review provisions puts it plainly: where the tribunal finds the market rent is higher than the landlord asked, the rent still does not rise beyond the landlord's figure.
• No backdating. The new rent runs from the date of the tribunal's determination, not the date on the notice. If your case takes four months, you pay the old rent for those four months and owe nothing extra afterwards.
• A hardship deferral. Where the increase would cause undue hardship, the tribunal can push the start date back by up to a further two months.
• No retaliation route. Section 21 no-fault eviction is abolished. Your landlord cannot serve notice because you challenged the rent.

One caveat worth knowing: the government reserved a power to reintroduce backdating by regulation if the tribunal is swamped. Commentary from spring 2026 indicates that power had not been exercised and no regulations laid. Check before you rely on it.

Read the notice before you read the number

Half the Section 13 notices circulating in London are served by agents who are still adjusting to the new regime. An invalid notice is worth more to you than a good comparables case, because it means no increase at all until a fresh one is served with a fresh two months.

Check, in this order:

1. Is it Form 4A? Anything served since 1 May 2026 on the old Form 4 is the wrong prescribed form. Agents recycling last year's template is a real problem, not a theoretical one.
2. Is the effective date at least two months after service? Count from the date you actually received it, not the date typed at the top. If it was posted, allow for deemed service.
3. Has it been 12 months? If your rent went up in, say, October 2025, the next increase cannot take effect before October 2026. Fifty-two weeks, not "next calendar year".
4. Does the new rent start at the beginning of a rental period? It has to line up with your period, and under the Act rental periods must be monthly (or 28 days), with non-compliant periods converting to monthly automatically.
5. Are the names, address and current rent right? A wrong current rent figure or a landlord named as the agent's trading company can be fatal.

If something is wrong, do not phone the agent to point it out. That invites a corrected notice by return. Note it, and raise it in your tribunal application, where the validity point is preserved.

The deadline is the whole game

You must apply to the First-tier Tribunal (Property Chamber) before the date the new rent is due to take effect. Not before the hearing, not within 28 days of anything. Before that date. Miss it and the increase simply happens, whatever the merits.

The form is Rents 1, the tenant's application referring a rent notice to the tribunal. It replaces the older form name you may still see in out-of-date guidance. Guides to the current process, including RentCtrl's, describe submitting the application free to preserve the deadline, with a £47 processing payment to follow. Confirm the current fee on GOV.UK before you send anything, because tribunal fees move.

Timings vary and the sources disagree honestly. Properteer's 2026 guide describes a typical paper determination taking six to twelve weeks. RentCtrl reports that contested cases going to an oral hearing are running at roughly six to nine months from application to decision, given the volume the tribunal has seen since May. Assume a paper determination unless the tribunal calls a hearing, and be pleased if it is quick. You are paying the old rent throughout either way.

Written reasons are not issued automatically. Request them within a month if you want them. Appeals go to the Upper Tribunal (Lands Chamber) on points of law only, within 28 days.

Building the borough case

The tribunal decides what the property would let for on the open market, on comparable evidence, disregarding improvements you paid for and your personal circumstances. Panels include RICS-qualified surveyor members who apply their own knowledge of the local market, so a case built on real borough data lands better than one built on grievance.

Two free sources do most of the work.

The London Rents Map, run by the Mayor's office, gives average monthly private rents by borough and bedroom count. Since its rebuild it draws on the ONS Price Index of Private Rents rather than advertised asking prices, which matters: it reflects achieved rents across new and existing tenancies. City of London estimates are not published because the sample is too thin.

The ONS Price Index of Private Rents gives you the direction of travel. The July 2026 release, covering the 12 months to June 2026, put average UK private rent at £1,388, up 3.3%, with London the lowest-inflation English region at 2.2%. Average London rent in June 2026 was £2,302, against £2,252 a year earlier.

The borough spread is where a London case is won. ONS data for the 12 months to May 2026 shows how wide it is:

If you rent in Westminster and your landlord wants 6%, the ONS index says the borough moved backwards over the year. That single line, with the source named and a screenshot attached, is a stronger opening than anything you can write about your boiler.

If you rent in Lambeth, be realistic. The ONS local area page for Lambeth records average private rent at £2,523 in June 2026, up 5.1% from £2,401 a year earlier, with flats and maisonettes up 5.0%. A 5% increase there is defensible. Your case then has to be about the specific flat: bedroom count, floor, condition, EPC rating, whether the second bedroom fits a bed. Pull four or five genuine comparables from the same postcode district, same property type, listed within the last three months, and print them with dates.

Condition arguments carry weight. If your flat is poorly insulated or the EPC is weak, that is a market factor a surveyor member will recognise, and it sits alongside the separate leverage renters now have from energy retrofit rules.

Why your agent's number is a new-let number

When an agent tells you rents are up 6%, they are almost certainly quoting HomeLet. Its Rental Index for July 2026 has London rents 6.0% higher than a year earlier. Zoopla's June 2026 report gives UK new-let average rent of £1,321, up 2.1%, with London rental inflation at 2.2%.

Here is the point to make, calmly, in writing.

HomeLet's index is built from tenant referencing carried out for letting agents. It measures rents agreed on new tenancies. It is a measure of what someone moving in this month pays, which is systematically higher than the achieved rent across the whole stock, because new lets reprice to the top of the market and sitting tenancies do not. The ONS index measures new and existing tenancies together using a fixed-basket method, which is why it produces 2.2% for London where HomeLet produces 6.0%.

Section 13 is about the open market rent for your property. That is a real market question and new-let evidence is relevant to it. But an index built purely from new lets, quoted at borough-blind city level, is weak evidence next to ONS borough figures and five local comparables for the same flat type. Say so.

A line that works with agents: "I've had the notice. I've checked the ONS Price Index of Private Rents for the borough and the London Rents Map for two-beds in SW9, and both put the figure below your proposal. HomeLet is a new-let index and doesn't reflect achieved rents on existing tenancies. I'd rather agree a figure than file a Rents 1, but I will file before the effective date if we can't."

Keep it in email. Two months of contemporaneous correspondence showing you engaged reasonably is useful in a bundle, and a clean payment record is useful too, which is one practical argument for paying rent through a system that produces a proper audit trail.

Doing it this week

Diary the effective date on the notice and set a reminder for three weeks before it. Photograph the notice and the envelope. Screenshot the London Rents Map entry for your borough and bedroom count today, because the map updates monthly and you want the figure that applied when the notice was served. Save five comparables as PDFs, dated. Draft the Rents 1 now and hold it.

Then send the email. Roughly a third of London landlords, faced with a tenant quoting the correct ONS series and a deadline, will meet in the middle rather than spend six months waiting on a tribunal that can only give them what they already asked for, starting later than they wanted.