Landlords who haven't touched rents since 2022 are sitting on gaps of 15% or more. The mechanism to close that gap is available now. Most of them just don't know how to use it.
What Has Happened?
The Renters' Rights Act abolished fixed-term assured shorthold tenancies in England on 1 May 2026. Every private tenancy now runs as a periodic assured tenancy: no end date, no built-in renewal window, no contractual rent review clause that a landlord and tenant agreed between themselves. That last point is the one most investors have missed.
Before 1 May 2026, landlords had two informal rent management routes alongside the statutory one. They could offer renewal at a higher rent (the tenant either accepted or left at the end of the fixed term), or they could rely on a contractual review clause embedded in the tenancy agreement. Both are gone. From 1 May 2026, the Housing Act 1988 provides the only route: Section 13, served on prescribed Form 4A.
Section 13 notices were already the correct mechanism for periodic tenancies before the Act. The changes made by the Renters' Rights Act are: a new prescribed form (Form 4A replaces old Form 4), a longer notice period (two months for all periodic tenancies, up from one month for monthly lets), and new rules governing what the First-tier Tribunal can and cannot do if a tenant challenges the proposed increase.
The net effect is that every landlord in England managing assured tenancies is now working to the same statutory process. Some have been doing this correctly for years. Many haven't, because they had workarounds that no longer exist.
Why This Matters to UK Property Investors
A significant number of private tenancies in England carry below-market passing rents. With rents rising sharply between 2021 and 2025 before flattening in Q1 2026, a tenant who moved in at £700 a month in late 2022 and hasn't had a formal review may now be paying £780 while comparable properties on the same street list at £920. That gap has two consequences for landlords, both of them avoidable.
The first is straightforward lost income. £140 a month below market rent is £1,680 a year. On a portfolio of five properties in that position, that's £8,400 of annual rent you're entitled to but not receiving. The statutory mechanism to close it has always existed. The difference now is it's the only mechanism.
The second consequence hits at refinancing. Buy-to-let mortgage stress tests use passing rent as the baseline, not market rent. A lender assessing a £150,000 property at a typical higher-rate-taxpayer requirement of 145% rental cover against a notional 6.5% rate needs around £887 a month to justify a £100,000 interest-only mortgage. A property sitting at £780 passing rent doesn't clear that test regardless of what the street commands. Investors with below-market rents are approaching their next refinance with a constraint they could eliminate. Form 4A is how you do it.
The two-month notice period matters for cash flow planning too. Under the old rules, a monthly periodic tenancy needed one month's notice. Now it's two. A notice served today (22 May) cannot produce a rent increase before 22 July at the earliest. Factor that into your refinancing timeline if the passing rent number is part of the calculation.
The Risks Investors Need to Understand
The most common error is using the wrong form. Form 4 was valid before 1 May 2026. It is not valid for notices served after that date. Many landlord template libraries, lettings agent admin packs, and older property management software still carry the old form. If you're using a template downloaded before April 2026, check whether it says Form 4 or Form 4A before serving it. An invalid notice buys you nothing. The tenant doesn't have to respond to it, the rent stays the same, and you've lost two months.
The 52-week rule is the second trap. A valid Section 13 notice cannot be served if fewer than 52 weeks have passed since the start of the rent period that resulted from the last Section 13 notice, or since the tenancy began. A landlord who served a notice in October 2025 cannot serve another before October 2026. When you buy a tenanted property, ask specifically when the last rent review was and whether a compliant notice was served at the time. That date governs your first opportunity to move the rent.
The first-year restriction applies separately. No rent increase is permitted during the first 12 months of a tenancy, regardless of notice timing. A tenant who moved in on 1 October 2025 cannot receive a valid Form 4A notice before 1 October 2026, even if the 52-week rule on previous reviews would otherwise allow it.
The tribunal change cuts both ways and most landlords misread it. The First-tier Tribunal (Property Chamber) cannot set a rent higher than the figure you proposed in your Form 4A notice. That is protection for landlords: if your research is solid and your proposed rent is the genuine market rate, the tribunal cannot award the tenant a higher figure. But the corollary matters: if the tribunal assesses open market rent as lower than what you proposed, it sets the lower figure and that becomes the binding rent. Proposing a figure above what comparables support is not a negotiating tactic. The tribunal will look at evidence of local comparable rents, and it will set what it finds, up to but not above your stated amount. If a tenant doesn't challenge and simply pays the proposed increase, the higher figure stands. The risk is in proposing a speculative number and then having a tenant call your bluff.
On timing: if a tenant does challenge at tribunal, the old rent continues until the decision is issued. The new rent applies from the decision date, not from when the notice was served. In areas where First-tier Tribunal Property Chamber is processing rent challenge applications in around two to four months post-filing, the gap between serving a notice and seeing the new rent is potentially five to six months total. Plan accordingly.
Where the Opportunity Could Be
Properties with below-market passing rents trade at a discount. Sellers price that in. The discount is often bigger than the income gap warrants, because most sellers don't model the Form 4A route to market rent as part of the exit price negotiation. They just know the rent looks low and they knock something off.
In Birmingham B6, B21 and B23, rents on two-bed terraces have moved from around £700 to £850 a month since 2022. A landlord exiting with a sitting tenant at £720 who signed three years ago will sometimes price that 15% income gap into the asking price as a 10% price reduction (or more) on the property. Buy it, confirm the review date was over 52 weeks ago, serve Form 4A within weeks of completion, and you're at market rent before your first mortgage payment lands. The two-month wait is baked into the acquisition plan rather than discovered afterwards.
Leeds LS4 and LS6, around Burley Road and Cardigan Road, have a similar profile. Salford M7 and M8 too. These are not exotic locations. They're mid-yield northern markets where the gap between passing rents on older tenancies and current market rents is predictable, verifiable against Rightmove and Zoopla comparable data, and closeable using a statutory process that has been in the law since 1988. The knowledge gap is that most buyers don't factor this into the acquisition model at all.
For investors refinancing existing portfolios, this is the most direct way to improve the stress test position before approaching a lender. Run the review dates across the portfolio, identify which properties are eligible, and serve all the Form 4A notices simultaneously. Two months later the passing rents move. That changes the refinancing numbers without selling anything, without buying anything, and without any lender conversation before the rent has actually changed.
Arsh's Investor View
I've been managing tenancies for over 25 years. The shift from "renew at a higher rent when the fixed term ends" to "serve Form 4A every year or the rent drifts" is a genuine operational adjustment. I'd be lying if I said it didn't add admin. It does.
But I'd also say this: most landlords who are worried about the new rent increase process have already been leaving money on the table for years. I've met investors with five or six properties who haven't formally reviewed a single rent since 2021. Not because they couldn't. Because they didn't like the conversation, because they assumed the tenant would leave, because they told themselves they'd do it "next year." Section 21 was the backstop that made passivity feel safe. That backstop is gone.
What I've started doing: reviewing Form 4A eligibility dates across the portfolio in January each year, the same way I review mortgage renewal dates. If a property's review date falls between January and March, I serve the notice in January to catch the rent from March. No gaps. No discussions about "what feels reasonable." The form goes out, the comparable evidence is in the file, and we move forward.
On the tribunal: I've not yet had a tenant challenge. I'd expect that to change as awareness of the £47 challenge fee and the "no backdating" protection grows among tenants. If it happens, I'm not bothered, provided I've proposed the right number in the first place. The tribunal can't go above my proposed figure. If I've done my research and proposed accurately, I'm well placed. The risk is in landlords proposing speculative amounts and then losing at tribunal on the evidence. Don't do that.
How Property Investor App Can Help
Understanding local market rents before you serve a Section 13 notice, or before you buy a tenanted property with a below-market rent, is the foundation of the whole process. Property Investor App lists live UK BTL, HMO, BRRR and regeneration deals with rental income data included, which lets you calibrate passing rents against what the current market supports before you instruct a solicitor or put pen to Form 4A. If you're looking at below-market-rent stock in Birmingham, Leeds, Sheffield or Salford, PIA gives you enough deal flow to cross-check pricing and income assumptions without trawling multiple portals separately.
Key Takeaways
- From 1 May 2026, Form 4A (Section 13) is the only valid rent increase mechanism for assured tenancies in England. The old Form 4 and any contractual rent review clauses are no longer valid.
- The notice period is two months for all assured periodic tenancies. A Form 4A served on 22 May takes effect no earlier than 22 July.
- Maximum one rent increase every 52 weeks. No increases permitted in the first year of a tenancy. Check the last review date before buying tenanted stock.
- Tenant challenge fee at the First-tier Tribunal is £47. The tribunal cannot set rent above the landlord's proposed figure. If unchallenged, the proposed rent stands.
- No backdating: if a tenant challenges, the existing rent continues until the tribunal decides, and the new rent applies only from the decision date.
- Properties with below-market passing rents often sell at a discount. The Form 4A route to market rent is a predictable, statutory process you can build into an acquisition plan.
Frequently Asked Questions
My tenant has been on the same rent since 2022. Can I increase it?
Yes, if at least 52 weeks have passed since the start of the current rent period and the tenancy has been running for more than 12 months. Serve Form 4A with two months' notice proposing the new rent. The tenant can accept (pays the new rent when the notice takes effect), challenge at the First-tier Tribunal for £47 (the tribunal sets the open market rate, up to but not above your proposed figure), or ignore the notice (in which case your proposed rent stands once the two months expire). Download the current Form 4A from gov.uk before serving.
Can I just write my tenant a letter asking for more rent?
No. From 1 May 2026, any rent increase on an assured tenancy in England that is not served via a valid Form 4A Section 13 notice is not enforceable. A letter, a WhatsApp, a verbal agreement, or a contractual rent review clause embedded in the tenancy agreement are all invalid as standalone mechanisms. If your tenant agrees informally to pay more and simply does so, that does not create a binding obligation. The only route that creates a legal obligation is the prescribed form.
What happens if my tenant challenges the rent increase at the First-tier Tribunal?
The existing rent continues while the case is pending. The tribunal assesses open market rent based on comparable evidence and sets a figure. That figure cannot be higher than the amount you proposed in the Form 4A notice, but it can be lower if the tribunal finds comparables support a lower rate. The new rent applies from the tribunal's decision date, not from the date the original notice took effect. There is no backdating under the Renters' Rights Act rules. The tenant's application fee is £47 with no additional hearing charge.
Can I increase the rent immediately when I buy a property with sitting tenants?
Not immediately. The 52-week rule applies to the tenancy's rent history, not to who owns the property. If the previous landlord served a valid Section 13 notice eight months ago, you cannot serve another for at least four more months. If the tenancy has never had a formal Section 13 review, the clock runs from the tenancy start date or from when the rent was last changed by a valid notice. Ask for the tenancy paperwork and rent history as part of your due diligence before exchange.
My tenancy has a rent review clause built in. Does that still apply?
No. From 1 May 2026, the statutory Section 13 process is the only valid mechanism for rent increases on assured tenancies. Contractual review clauses agreed between landlord and tenant are superseded by the statute. You cannot enforce a contractual clause as the basis for a rent increase. If you want to increase the rent, you serve Form 4A. The clause is not void, it simply cannot be used as a substitute for the prescribed notice process.
