What makes a Section 13 notice invalid?
A Section 13 rent increase either works or it does not – there is no half-valid notice. Under the Renters’ Rights Act the consequences of getting it wrong are expensive: the increase does not happen, and the landlord has to start again. This guide sets out the errors that void a Form 4A notice in practice, why each one fails, and what happens when a notice is defective.
Last reviewed: 1 July 2026 · Reflects the Renters’ Rights Act 2025, in force from 1 May 2026Why validity is all-or-nothing
Since 1 May 2026, the Section 13 procedure on the prescribed Form 4A has been the only way to increase the rent on an assured periodic tenancy in England. Rent review clauses no longer have any effect, and informal increases agreed outside the procedure are not enforceable. That puts all of the legal weight on the notice itself – and a notice that breaches any one of the requirements is invalid in its entirety. A single wrong date is enough to void it, however carefully the rest is completed.
The five errors that void notices
These are the mistakes that most commonly invalidate notices in practice. Every one of them means serving a fresh Form 4A and waiting out a new two-month notice period – typically a two-to-three-month delay and, on an average increase, hundreds of pounds of lost rent.
| Error | Why it fails |
|---|---|
| Wrong or outdated form | Only the current prescribed Form 4A from GOV.UK is valid. An old Form 4 template – often built around the previous one month’s notice – or a homemade version is invalid even if it contains identical information. |
| Effective date less than two months after service | The Renters’ Rights Act doubled the minimum notice to two months. A notice giving any less – including where deemed service quietly eats into the period – is invalid. |
| Effective date not on a rent due date | The new rent must begin on the first day of a rent period – the contractual rent due date. A mid-period date, or the date the tenant happens to pay, is invalid. |
| Less than 52 weeks since the last increase | Breaches the once-a-year rule. Measure from the date the previous increase took effect, not the date the previous notice was served. |
| Ignoring deemed service when posting | If the notice arrives later than assumed, the two months can fall short by a day or two. Build in a buffer for postal service and keep proof of service. |
The date traps in more detail
The wrong day: Mooney v Whiteland
The rent period rule is stricter than it looks. The effective date must be the day rent is contractually due under the tenancy agreement – not the day the tenant usually pays. In Mooney v Whiteland, a rent increase notice was held invalid because it used the day the tenant habitually paid rather than the contractual due date. If your agreement says rent is due on the 1st, the increase can only take effect on a 1st, even if the tenant has always paid on the 5th.
Too early by a day
The two months’ notice and the rent period rule interact in a way that catches people out. Adding exactly two months to the service date almost never lands on a rent due date, so the effective date has to roll forward to the next due date after the two months have passed. Pick the due date that falls just before the two months are up and the notice gives less than the minimum notice – and is void.
Breaching the 12-month gap
Rent can only be increased once a year. The new rent cannot take effect until at least 52 weeks after the previous increase took effect, or 12 months after the tenancy started where the rent has never been increased. The common slip is measuring the gap from the date the last notice was served rather than the date the last increase actually took effect. The 12-month rule explained works through this in detail.
Example: the roll-forward trap
Rent is due on the 10th. The landlord serves Form 4A on 15 August, and writes 10 October as the effective date. Two months from service is 15 October – so 10 October gives less than two months’ notice and the notice is invalid. The earliest valid date was 10 November. The landlord now has to serve a fresh notice and wait out a new two-month period.
What happens when a notice fails
There is no mechanism to patch up a defective notice after it has been served. If the form is wrong or a date is out, the notice simply does not take effect, and the landlord’s only route is to serve a fresh, correct Form 4A – which restarts the two-month clock from scratch. For a landlord, that is a delay measured in months; for a tenant, it means the current rent continues until a valid notice runs its course. Either way, the cheapest notice is the one that is right the first time.
To get it right before it goes out, follow our step-by-step guide on how to serve a Section 13 rent increase, and use the Section 13 date calculator to confirm the effective date.
Frequently asked questions
What happens if the notice is invalid?
The rent increase does not take effect. The landlord must serve a fresh Form 4A with a correct date, restarting the two-month notice period. A defective notice cannot be fixed after the event.
Does using the wrong day for the effective date really void it?
Yes. The new rent must take effect on the contractual rent due date. In Mooney v Whiteland a notice was invalid because it used the day the tenant habitually paid rather than the day rent was due.
Can a landlord correct a mistake on a served notice?
Not by amending it after service. The practical fix is to serve a fresh, correct Form 4A and start the notice period again.
How do I check whether the dates are valid?
Enter the service date, contractual rent due date and date of any previous increase into the Section 13 date calculator. If the effective date on the notice is earlier than the result, the notice may be invalid.
Is this legal advice?
No. This page is general guidance. For advice on a specific notice, and to confirm the current prescribed form, check GOV.UK or speak to a solicitor or professional adviser.
Disclaimer: TenancyTools.uk provides general guidance and calculation tools, not legal advice. The Section 13 rules described on this page apply to assured periodic tenancies in England under the Housing Act 1988 as amended by the Renters’ Rights Act 2025. Different rules apply in Wales, Scotland and Northern Ireland. While we work hard to keep every page accurate and up to date, you should verify dates and requirements against the current prescribed form and guidance on GOV.UK before serving or responding to a notice, and take professional advice where the outcome matters.