Section 13 Rent Increase Date Calculator
Work out the earliest date a rent increase can lawfully take effect under the Renters’ Rights Act. The calculator applies the two months’ notice rule, the rent period rule and the 12-month gap rule to the dates you enter – the three date rules that most commonly void a Form 4A notice.
Last reviewed: 1 July 2026 · Reflects the Renters’ Rights Act 2025, in force from 1 May 2026Calculate the earliest valid effective date
How the three date rules work
Since 1 May 2026, a Section 13 notice on the prescribed Form 4A has been the only way to increase the rent on an assured periodic tenancy in England. Rent review clauses in tenancy agreements no longer have any effect, and informal increases agreed outside the Section 13 procedure are not enforceable. That puts all of the legal weight on getting the notice right – and the part landlords most often get wrong is the date.
Three separate rules control the effective date, and the notice must satisfy all of them at once:
- The two months’ notice rule. The tenant must be given at least two months’ notice before the new rent takes effect. The Renters’ Rights Act doubled this from the previous one month, so any old template referring to one month’s notice is out of date and will produce an invalid notice.
- The rent period rule. The new rent must take effect on the first day of a rent period – the day rent is contractually due. If rent is due on the 10th of each month, the increase can only start on a 10th. It is the contractual due date that counts: in Mooney v Whiteland, a notice was held invalid because it used the day the tenant habitually paid rather than the day rent was actually due.
- The 12-month gap rule. 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, where the rent has never been increased, at least 12 months after the tenancy began.
The interaction between the first two rules is the classic trap. Adding two months to the service date almost never lands exactly on a rent due date, so the effective date must roll forward to the next due date after the two months have passed. In practice the true notice period is usually somewhere between two and three months, and picking a date even one day too early makes the whole notice invalid.
Worked examples
Example 1: the classic roll-forward
Rent is due on the 10th of each month. The landlord serves Form 4A on 15 August. Two months from service is 15 October – but 10 October is before that, so it fails the notice rule. The earliest valid effective date is 10 November. Writing 10 October on the form would void the notice entirely, and the landlord would have to start again with a fresh two-month clock.
Example 2: the 12-month rule bites instead
Rent is due on the 1st. The last increase took effect on 1 March 2026. The landlord serves a new notice on 1 June 2026. Two months from service is 1 August – but 52 weeks from 1 March 2026 runs to 28 February 2027, so the notice rule is not the binding constraint. The earliest valid effective date is 1 March 2027. Serving very early is legal, but the effective date still cannot beat the 12-month gap.
Example 3: a new tenancy’s first increase
A tenancy started on 1 June 2026 with rent due on the 1st, and the rent has never gone up. The first increase cannot take effect before 1 June 2027 – 12 months after the tenancy began – no matter how early the notice is served. To hit 1 June 2027 exactly, the landlord must serve Form 4A on or before 1 April 2027.
Five date errors that void a Section 13 notice
These are the mistakes that most commonly invalidate notices in practice. Every one of them means starting the process again from scratch – typically a two-to-three-month delay and, on an average rent increase, hundreds of pounds of lost income.
| Error | Why it fails |
|---|---|
| Effective date less than two months after service | Breaches the minimum notice period introduced by the Renters’ Rights Act. Old Form 4 templates built around one month’s notice are the usual culprit. |
| Effective date is not the start of a rent period | The new rent must begin on 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 took effect | Breaches the once-a-year rule. Measure from the date the previous increase took effect, not the date the previous notice was served. |
| Using a homemade or outdated form | Only the current prescribed Form 4A from GOV.UK is valid. A homebrew version is invalid even if it contains identical information. |
| Ignoring deemed service when posting | If the notice arrives later than assumed, the two months may fall short by a day or two. Build in a buffer for postal service, and keep proof of service. |
What happens after the notice is served
If the tenant accepts the increase, the new rent is simply payable from the effective date. If they think it is above the open market rate, they can refer it to the First-tier Tribunal at any point before the effective date. The tribunal’s role is to determine the open market rent – and under the Renters’ Rights Act it cannot set the rent higher than the figure on the notice, which removes the risk that previously deterred tenants from challenging. For landlords, the practical defence is straightforward: propose a figure supported by genuine local comparables, and keep the evidence.
A tribunal referral also delays the increase, so realistic figures served correctly the first time are worth more than ambitious figures that invite a challenge. Both sides can find the challenge process, deadlines and what the tribunal can decide in our guide on how tenants challenge a rent increase at the First-tier Tribunal.
Related guides
For the process behind the dates, read our step-by-step guide to serving a Section 13 notice and the checklist of what makes a Section 13 notice invalid. The 12-month rule explained covers the 52-week gap in more depth, and rent review clauses are void sets out why Section 13 is now the only route.
Frequently asked questions
How much notice must a landlord give for a rent increase in 2026?
At least two months, using a Section 13 notice on Form 4A. Because the new rent must also start on a rent due date, the real-world gap between service and the increase is usually between two and three months.
Can a landlord still use a rent review clause in the tenancy agreement?
No. From 1 May 2026, rent review clauses in assured tenancy agreements have no effect. Section 13 with Form 4A is the only valid route, whatever the agreement says.
How often can the rent be increased?
Once every 12 months. The new rent cannot take effect until at least 52 weeks after the previous increase took effect, or 12 months after the tenancy started if the rent has never been increased.
What happens if the date on the notice is wrong?
The notice is invalid and the increase does not take effect. The landlord has to serve a fresh Form 4A with a correct date, restarting the two-month clock. Date errors are the most common reason Section 13 notices fail.
Can a tenant challenge the proposed rent?
Yes – by referring it to the First-tier Tribunal before the effective date. The tribunal decides the open market rent and cannot set it higher than the landlord’s proposed figure.
Is this legal advice?
No. The calculator applies the statutory date rules to the dates you enter and is provided as general guidance. For advice on your specific situation, 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.