What makes a rent increase notice invalid

Last updated June 2026

Why this matters

An invalid notice doesn't just fail quietly — it means the rent doesn't go up, and you have to serve a fresh notice and wait the full two months again. Worse, you may not realise until the tenant points it out. Here are the usual reasons a Section 13 / Form 4A notice is thrown out.

The common mistakes

• Wrong or outdated form. Anything other than the current Form 4A — including a custom letter — is invalid.
• Less than two months' notice. The new rent must start at least two months after service.
• Effective date mid-period. It must fall at the start of a tenancy period (your rent day), not any date you like.
• Increasing too soon. No more than once every 12 months.
• Forgetting service time. Posting a notice is usually treated as served two working days later, which can push your earliest valid date back.
• Wrong contact address. The landlord's address for service must be complete so the tenant can respond.

How to avoid it

The reliable fix is to let the dates be calculated for you and to serve on the current prescribed form. Our free generator checks the two-month period, the once-a-year rule, and the tenancy-period date, then produces a ready-to-serve Form 4A — so the notice can't be voided on a technicality.