Raising the rent on a tenancy has never been completely straightforward. There are rules, notice periods, and processes to follow. But most landlords in Southampton have managed it through a combination of renewal conversations, informal agreements, and the occasional formal notice when things needed to be formalised.
From 1 May 2026, that flexibility disappears. There is one way to increase rent, and one way only. Everything else becomes unenforceable: rent review clauses written into your tenancy agreement, informal arrangements agreed between landlord and tenant, anything other than the statutory process.
It’s worth understanding exactly how this works before you need to use it, because the new process has some features that will catch landlords off guard.
The one route that remains: section 13 and Form 4A
From 1 May 2026, every rent increase in the private rented sector must go through the section 13 notice procedure using a new prescribed form called Form 4A. The government has confirmed this form will be available on GOV.UK from 1 May itself. If you want to serve a notice that takes effect from June or July, you’ll need to move quickly once it’s published.
The notice requirements are clear. You must give at least two months’ notice before the new rent takes effect, which is double the current one-month requirement. The increase can only take effect at the beginning of a rent period, which under the new rules will always be monthly. You cannot increase rent more than once in any twelve-month period. And the increase cannot take effect until at least 52 weeks after the date the rent was last increased using section 13.
That last point matters for landlords who have recently put the rent up. If you served a section 13 notice in October 2025 that took effect in December 2025, you cannot issue another notice that takes effect before December 2026, regardless of when you serve it.
What happens to rent review clauses in existing agreements
This is one of the most common questions we’re hearing from landlords right now, and the answer is unambiguous.
Any clause in an existing tenancy agreement that automatically increases or calculates rent becomes null and void from 1 May 2026. It doesn’t matter whether it’s linked to RPI, CPI, a fixed annual percentage, or any other mechanism. The government guidance is explicit: any rent increase agreed before 1 May but due to take effect after it will not be permitted. You cannot rely on a review clause that was scheduled to operate in August 2026. That clause will have no legal force.
If you were planning a rent increase that was already baked into your tenancy agreement, you need to know that the section 13 process is now the only route, and you need to allow two months’ notice from when Form 4A becomes available.
There is one nuance worth knowing. If a landlord serves a valid section 13 notice, they can subsequently agree a lower amount with the tenant, but they cannot agree a higher amount. The notice acts as a ceiling, not a floor. And critically, informal verbal agreements to increase rent, made outside the notice process entirely, will not be enforceable.
How often can you realistically increase rent?
Once a year, and not within the first twelve months of a new tenancy. That second point is new. Under the current rules, there’s no restriction on serving a section 13 notice early in a tenancy. From May, you cannot issue a notice that would take effect within the first year.
For most landlords with long-term tenants, the once-a-year rhythm won’t feel much different from current practice. For landlords who’ve had below-market rents and were hoping to catch up quickly, this changes the calculation. You get one increase per year, it must be to market rate, and you need to be able to justify it.
For new tenancies starting after 1 May, there’s a further consideration. If a tenant thinks the initial rent agreed when they moved in was above market rate, they have the right to apply to the First-tier Tribunal for what’s called an initial rent determination in the first six months. This is a new power that didn’t previously exist, and it means that even rent agreed at the start of a tenancy isn’t entirely beyond challenge.
Tenant challenges and the tribunal: the honest picture
The new system makes it easier for tenants to challenge rent increases, and it’s worth being clear-eyed about what that means.
From 1 May, tenants can challenge any section 13 notice by applying to the First-tier Tribunal before the new rent takes effect. The tribunal will determine the market rent, the amount the property would achieve if freshly advertised, and that figure becomes the rent, whether it’s higher or lower than what the landlord proposed. Under the new rules, the tribunal cannot set a rent higher than what the landlord originally proposed. That removes one risk that currently exists under the old system, where a tenant challenging a notice could end up with a higher rent than the landlord asked for.
The more important dynamic is this: appealing a notice delays the increase, sometimes by months if tribunal backlogs are significant. The new rent cannot take effect until the tribunal makes its determination. There is concern in the industry that this will incentivise tenants to challenge increases simply as a delay tactic, even where the proposed rent is entirely reasonable. The government has indicated it reserves the right to backdate increases if the tribunal becomes overwhelmed with cases, but that’s not a guarantee landlords can plan around.
In practice, what this means for Southampton landlords is straightforward. If you’re proposing a rent increase, make sure you can evidence it with comparable market data. Keep records of similar properties currently advertised to let in the same area, at roughly the same size and specification. If your proposed rent is genuinely in line with the local market, a tribunal challenge is unlikely to go badly for you.
The Southampton rental market context
Average private rents in Southampton reached £1,238 per month in January 2026, up 4% on the previous year and above the national trend. One-bedroom properties have risen faster, at 4.6% annually. The Southampton market has its own dynamics that national headlines don’t capture, driven in part by persistent undersupply in the lettings sector and consistent demand from university students, NHS and port economy workers, and young professionals.
What this means practically is that landlords with properties rented below current market levels have legitimate room to propose increases that a tribunal would uphold. The section 13 process, used correctly with good market evidence, is not a barrier to sensible yield management. It’s a formalisation of something that was always supposed to be evidence-based.
Where landlords are more exposed is where rents have been pushed above market rate in recent years, or where a proposed increase outpaces what comparable properties are achieving. Those are the situations where a tenant challenge becomes both more likely and more consequential.
What to do before May
There are three things worth doing now, before the new rules land.
First, audit your portfolio for any properties where a rent review clause was scheduled to operate in the second half of 2026. If you were relying on that clause, you now need to plan a section 13 notice using Form 4A once it becomes available and budget for the two-month notice period.
Second, if you haven’t reviewed your rents against the current market recently, do it now. Understanding where your rents sit relative to comparable properties gives you the information you need to serve a credible section 13 notice and to manage any challenge confidently.
Third, consider what your record-keeping looks like. The section 13 process is about documentation: notice dates, last increase dates, comparable market evidence. Landlords who treat this as a routine administrative exercise, with a simple system in place, will find it far less stressful than those who try to manage it ad hoc.
We help landlords across Southampton manage rent reviews, evidence market comparables, and navigate the section 13 process as part of our full management service. If you want to talk through what the new rent rules mean for a specific property or portfolio, we’re here.
Speak to the Hunters Southampton lettings team
Whether you have one property or fifteen, the new rent increase rules represent a meaningful change to how your income stream is managed. We’re happy to sit down with any landlord in Southampton and go through the numbers: what your properties are achieving, what the market supports, and how to approach the new process with confidence.
Call us, email us, or come in for a conversation.
Hunters Southampton | hunters.com/southampton | 02380 987 720
*This post reflects our understanding of the Renters’ Rights Act as of March 2026. This is not legal advice. Always consult a qualified solicitor for guidance specific to your situation.
