Rent increase calculator: the earliest lawful start date
On an assured periodic tenancy, only a Section 13 notice on Form 4A can increase the rent: two months of notice, taking effect at the start of a rent period, no more than once in any 12 months. Enter your dates and this tool finds the earliest date a new rent can begin.
Assumes a monthly rent period. General information, not legal advice.
The three rules the tool applies
First, two months of notice: the new rent cannot start sooner than two months after the notice is served. Second, the start of a rent period: the new rent must begin on a day rent falls due, so the tool moves forward from the two month point to the next rent due date. Third, once in 12 months: where a previous increase took effect within the last year, the new rent cannot start until 12 months have passed since that date. The tenant can refer the proposed figure to the First-tier Tribunal before the start date. Why an informal letter cannot do this job is covered in the Form 4A guide, and the wider rules, including the ban on rent in advance beyond one period, are in rent in advance and the full guide to the Act.
Common questions
How do I increase rent on a periodic tenancy in 2026?
Only by a Section 13 notice on Form 4A: two months of notice, taking effect at the start of a rent period, no more than once in any 12 months.
Can I increase rent with a letter or email?
No. An informal letter cannot increase the rent on an assured periodic tenancy. The prescribed form is the only route.
Can the tenant challenge the new rent?
Yes. Before the start date the tenant can refer the proposed rent to the First-tier Tribunal, which then sets a market rent.
When exactly does the new rent begin?
On the first rent due date that falls at least two months after service, and at least 12 months after any previous increase took effect.
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Start my agreement →Frequently asked questions
What is the difference between mandatory and discretionary grounds?
A mandatory ground proved compels the court to order possession; a discretionary ground adds a reasonableness test the court decides on the circumstances.
What replaced the AST in 2026?
The assured periodic tenancy: open-ended, monthly, with possession only on Section 8 grounds and rent increases only via Section 13.