Rent Increase Calculator (Section 13 & CPI)
Model a proposed rent increase against CPI, market rent, and the new Section 13 / RRA rules — and check if the increase is likely to be challenged at the First-tier Tribunal.
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Assessment
Section 13 of the Housing Act 1988 (as amended by the Renters' Rights Act 2026) lets a tenant refer the increase to the First-tier Tribunal. The Tribunal sets rent at market level — never higher than your proposal.
Frequently asked questions
▸How often can I raise the rent under the Renters' Rights Act?
Once every 12 months, with at least two months' notice using a prescribed Section 13 form.
▸What is a 'reasonable' increase?
Aligned to local market rent. The First-tier Tribunal can cap a proposed rise to market rent — never higher.
▸Can I tie increases to CPI?
Not in the tenancy agreement under the new rules — rent review clauses to CPI/RPI/fixed amounts are unenforceable. Increases must go through Section 13.
▸What if the tenant refuses?
They can apply to the First-tier Tribunal within the notice period. The Tribunal sets rent at market level.
▸Does this work for periodic tenancies?
Yes — all assured tenancies are now periodic under the Renters' Rights Act (in force since 1 May 2026).
▸How do I evidence market rent?
Three comparable local listings on Rightmove, Zoopla and OnTheMarket — saved with dates and screenshots.
▸Can I increase mid-fixed term?
Fixed-term ASTs have been abolished by the Renters' Rights Act. Since 1 May 2026 every assured tenancy is periodic, so rent changes always follow the Section 13 route.
▸Is there a percentage cap?
Not a hard cap, but the Tribunal will benchmark against market. A 20%+ jump is high risk.
▸Can the tenant negotiate?
Yes — many landlords agree a compromise figure to avoid the Tribunal process.
▸Do I need a written notice?
Yes — Section 13 requires a prescribed form. We provide a template.