Rent increases

Form 4A Rent Increases: 5 Mistakes That Void Your Section 13 Notice

October 2026 · 9 min read · England private rented sector

There is now exactly one lawful way to increase rent on an assured periodic tenancy in England: the Section 13 procedure, using the official Form 4A. Contractual rent-review clauses are void, a letter doesn't count, an email doesn't count, and a conversation definitely doesn't count. The form is free on GOV.UK — but it's procedurally strict, and an invalid notice can't be patched up after service. You start again, with a fresh two-month clock.

Here are the five mistakes that kill most Section 13 notices, and how to avoid each one.

Mistake 1: Not using Form 4A at all

It sounds obvious, but old habits die hard. Landlords who used to agree increases by email or rely on a clause in the tenancy agreement sometimes still do. Under the Renters' Rights Act, those methods are legally void for assured periodic tenancies. If the tenant later disputes the increase — or simply stops paying the extra — you have nothing to stand on. Always download a fresh copy of Form 4A from GOV.UK (search GOV.UK for "Form 4A"); forms are updated over time, and an outdated version can itself invalidate the notice. Complete every field — a partially completed form is an invalid form.

Mistake 2: The 52-week trap

Rent can be increased at most once in any 12-month period — and that means 52 weeks from the date the last increase took effect, not "once per calendar year". A landlord who raised the rent effective 1 June 2026 and serves the next increase effective 1 May 2027 has acted too early, and the notice is void. Fifty-two weeks drifts against the calendar, so a landlord who diarises a fixed calendar date will eventually serve a few days early and invalidate the notice. Work from the last effective date plus 52 weeks, and when in doubt, add a few days' buffer. If you've never increased the rent, count from the date the first period of the tenancy began.

Mistake 3: The wrong start date

The new rent must take effect on the first day of a rent period — the date rent falls due each month — and at least two months after the tenant receives the notice. Both conditions must hold. A start date mid-period is void; a start date only seven weeks after service is void. And note the counting: the two months run from when the tenant receives the notice, not when you post it. First-class post is deemed served two working days later; email depends on what your agreement permits. Build in extra days rather than cutting it fine — a notice that's a day short fails just as completely as one that's a month short.

Mistake 4: Sloppy details on the form

The unglamorous errors: a tenant's name that doesn't match the tenancy agreement exactly, a missing flat number in the address, a rent figure expressed as a range or a percentage instead of an exact sum in pounds and pence. Every named adult tenant must be served individually. The figure must be determinate — the tenant has to know exactly what they're being asked to pay. Double-check the form against the tenancy agreement line by line before it goes out; errors are the most common reason rent-increase notices fail.

Mistake 5: A figure you can't defend

There is no statutory cap on the increase, but the proposed rent must reflect the open market rent — and the tenant can challenge it. Do your homework before you serve: pull three or four comparable local listings for similar properties, save them, and note the differences in size, condition and furnishing. This evidence is your defence if the tenant refers the increase for independent determination.

One development to watch: the government announced in October 2026 that rent-increase disputes will move from the First-tier Tribunal to the Valuation Office Agency. The transfer is not yet fully in effect at the time of writing — check GOV.UK for the current route before you serve, and keep your market-rent evidence regardless of which body decides.

The service routine that holds up

1. Confirm the 52-week gap and pick a start date on a rent-period boundary, at least two months out.
2. Research comparable rents and save the evidence.
3. Download a fresh Form 4A from GOV.UK and complete every field.
4. Serve every named tenant — email with read receipt plus first-class post is the belt-and-braces option — and record the date and method.
5. Diary the tenant's challenge window and your next eligible increase date (52 weeks on).

Not legal advice. This guide is general information for private landlords in England, written in October 2026. It is not legal advice and does not create a solicitor–client relationship. Housing law changes — check GOV.UK's guide to the Renters' Rights Act and your local council before acting, and take professional advice on your own circumstances.