What Is a Fair Rent Increase Under the Renters' Rights Act?
There is no legal cap on how much you can increase rent under the Renters' Rights Act 2025. The Act doesn't define "fair." What it does is give every tenant in England the right to challenge your proposed increase at the First-tier Tribunal (Property Chamber) — free of charge, with no risk of eviction for doing so.
That changes the calculus. Under the old rules, most tenants accepted increases because challenging them was rare and the landlord could serve a Section 21 notice in retaliation. From 1 May 2026, Section 21 is abolished, tribunal challenges are free, and the tribunal can delay the increase by up to 2 additional months if the tenant faces hardship. The question isn't "what's the maximum I can charge?" — it's "what increase can I defend with evidence?"
How rent increases work from 1 May 2026
The only valid method for increasing rent on an assured tenancy is the Section 13 process using the new Form 4A. Informal agreements — including written ones signed by both parties — have no legal effect.
The rules:
| Rule | Detail |
|---|---|
| Frequency | Once per 12-month period only |
| First year | No increase in the first 12 months of a tenancy |
| Notice period | 2 months minimum via Form 4A |
| Method | Section 13 / Form 4A only — contractual rent review clauses are void |
| Tenant response | Accept, negotiate, or refer to the First-tier Tribunal (free) |
| Tribunal power | Determines the "market rent" — can reduce or maintain current rent |
| Hardship provision | Tribunal can delay the effective date by up to 2 months |
For the step-by-step Form 4A process and worked examples, see our Form 4A rent increase guide.
What "market rent" actually means
When the tribunal assesses a challenged increase, it determines the open market rent for the property in its current condition. This is defined in Section 14 of the Housing Act 1988 (as amended by the RRA).
The tribunal considers:
- Rents for comparable properties in the same area
- The property's condition, size, location, and amenities
- The current local rental market
The tribunal does not consider:
- Improvements the tenant has made
- The landlord's mortgage costs or desired yield
- What the landlord paid for the property
This is a critical point: the tribunal doesn't care about your costs. If comparable 2-bed flats in the same postcode rent for £950/month and yours is currently at £900, the maximum defensible increase is roughly £50/month — regardless of whether your mortgage rate doubled.
What percentage is actually defensible?
There's no single "fair" number, but here's what the data shows for England in early 2026:
| Benchmark | Rate | Source |
|---|---|---|
| CPI inflation (Jan 2026) | ~3% | ONS |
| Average private rent increase (England, 12 months to Jan 2026) | ~8% | ONS IPHRP |
| Commonly cited "uncontested" increase range | 3–5% | Examples seen in published landlord guidance (as of early 2026) |
A 3–5% increase backed by local comparable evidence is unlikely to be challenged. A 10%+ increase without strong market data is very likely to trigger a tribunal referral — and from May 2026, tenants have nothing to lose by challenging.
How to build a defensible increase
The tribunal uses comparable evidence. So should you. Before serving a Form 4A notice:
1. Gather local comparables
Search major listing portals for properties matching yours:
- Same number of bedrooms
- Same postcode district (first 4-5 characters)
- Same property type (flat, terraced, semi-detached)
- Listed or let in the last 3 months
Record asking rents for at least 5 comparables. The ONS Index of Private Housing Rental Prices provides regional averages but the tribunal uses hyperlocal data — same street or estate is best.
2. Adjust for property condition
Your property's condition matters. If comparable flats have been refurbished and yours hasn't, the tribunal will discount your comparable evidence. Be honest about where your property sits relative to the comparables.
3. Calculate the proposed increase
Compare your current rent against the comparable median. If the median comparable rent is £1,050 and you're currently charging £950, a £100/month increase (10.5%) is defensible because it's supported by market evidence — even though 10.5% sounds high.
Conversely, if comparables are at £980 and you're at £950, a £30/month increase (3.2%) is all the evidence supports. Asking for £100 would be overturned at tribunal.
4. Document everything
Keep your comparable search results, screenshots of listings, and the ONS data you referenced. If the tenant challenges, you'll need this for the tribunal.
Worked example: a 2-bed flat in Bristol
| Factor | Detail |
|---|---|
| Current rent | £950/month |
| Tenancy start date | 1 June 2025 |
| First valid increase date | 1 June 2026 (12-month rule) |
| Form 4A served | 1 April 2026 (2 months' notice) |
| Comparable median (5 similar flats, BS3 postcode, let in Jan-Mar 2026) | £1,020/month |
Proposed increase: £950 → £1,020/month (7.4%).
Is this defensible? Yes — it's backed by 5 recent comparables in the same postcode district. The increase brings the rent to the local median, not above it.
What if the tenant challenges? The tribunal reviews the same comparable data. If they agree the market rent is £1,020, the increase stands. If they find the market rent is £990, they set it at £990 and the landlord can't challenge further.
Use the free Rent Increase Calculator to check when you can next increase rent on each property and calculate the 2-month notice period.
What happens if the tenant challenges
The process from 1 May 2026:
- You serve Form 4A with the proposed new rent and the date it takes effect (at least 2 months away)
- Tenant receives it — they have until the effective date to respond
- Tenant refers to tribunal — free application to the First-tier Tribunal (Property Chamber)
- Tribunal determines market rent — based on comparable evidence, not your proposal
- Tribunal sets the rent — this could be your proposed amount, the current rent, or anything in between
- Hardship delay — if the increase causes genuine hardship, the tribunal can delay the effective date by up to 2 additional months
Key changes from the current system:
- No retaliatory eviction risk — Section 21 is abolished, so tenants can challenge without fear of being served notice
- Tribunal can't exceed your proposal — they can reduce it but won't increase it above what you asked for
- One-way door — once the tribunal sets the rent, that's the rent. You can't serve another Form 4A for 12 months.
Common mistakes to avoid
Serving Form 4A too early. You cannot increase rent within the first 12 months of the tenancy. If the tenancy started 15 September 2025, the earliest Form 4A effective date is 15 September 2026 — and you need 2 months' notice, so serve by 15 July 2026.
Using the wrong form. Form 4 (the current version) will not be valid from 1 May 2026. You must use Form 4A. Monitor GOV.UK's assured tenancy forms page for the new form.
Relying on contractual clauses. Any clause in your tenancy agreement specifying when or how rent increases (e.g., "RPI + 2% on anniversary") is void from 1 May 2026. Section 13 / Form 4A is the only route.
Not keeping comparable evidence. If your increase is challenged and you can't produce evidence, the tribunal will determine market rent based on whatever data is available — which may result in no increase at all.
Multiple increases in 12 months. Only one Form 4A notice per tenancy per 12-month period. If you serve one and it's reduced at tribunal, you can't serve another to "top up" until the next 12-month window.
The strategic shift for landlords
Before the RRA, rent increases were largely a negotiation. Tenants who pushed back risked a Section 21 notice. That dynamic is gone.
From May 2026, every rent increase is potentially a tribunal case. The landlords who adapt fastest will:
- Set rents at market from the start — if your initial rent is below market, you'll face a larger catch-up increase that's more likely to be challenged
- Build a comparable evidence file for every property annually, even if you don't increase rent that year
- Time increases carefully — the once-per-year restriction means a mistimed increase locks you out for 12 months
For the full compliance picture, see the Complete Landlord Compliance Checklist. For all key dates and deadlines, check the RRA key dates timeline.
This guide covers rent increases under the Renters' Rights Act 2025 as it applies to assured tenancies in England only. This is not legal or financial advice. For specific questions about your situation, consult a solicitor or RICS surveyor.
Information is current as of the date shown above. We update this page when new guidance or secondary legislation is published.