The County Court judgment in Cassell & Cassell v Sidhu & Sidhu (October 2025) revisits the long-standing issue of Gas Safety Certificates (GSCs) and their impact on the validity of S.21 Notices. 

With the Renters Rights Bill’s impending commencement, S.21 Notices will soon be a thing of the past. However, this recent judgment, although not legally binding, will be of persuasive value until this time. 

Case background 

The case involved tenants appealing a possession order made under S.21 of the Housing Act 1988. 

The central issue was whether the pre-tenancy GSC did not comply with Gas Safety Regulations, rendering the S.21 notice invalid and preventing the landlords from recovering possession.

Although there was a pre-tenancy GSC, the section for ‘details of customer/landlord’ was left blank. The tenants argued that this invalidated the S.21 Notice and the Judge at first instance was wrong to make an order for possession. No issues were raised with the two subsequent GSCs that were obtained during the tenancy.
Judgment 

On appeal, HHJ Clark found that the pre-tenancy GSC was incomplete. The key question was whether this invalidated the S.21 Notice. The Judge found that the defect in the pre-tenancy GSC was remedied by the two later GSCs, both of which were compliant and served on the tenants before the S.21 Notice. The tenants’ appeal was therefore dismissed.

Impact of the Judgment

If followed, this decision suggests the following outcomes when a GSC is defective but later corrected:

1. Tenancy under 12 months: A defective GSC will invalidate a S.21 Notice unless it is corrected before the notice is served.

2. Tenancy between 12 and 24 months: The same as above - procedural defects to the GSCs will invalidate S.21 Notice unless remedied before serving the notice.

3. Tenancy over 24  months: the last two GSCs cannot contain any procedural defects. Earlier GSCs may contain procedural errors without impacting the validity of the notice.

The judgment opposes the view in Byrne v Harwood‑Delgado (2022) (heard by HHJ Bloom), which held that a defect in the pre‑tenancy GSC (such as the one in this case) cannot be rectified under any circumstances and therefore the landlord was precluded from recovering possession using the S.21 procedure.

As both of these appeals were heard in the County Court, the respective decisions will not be legally binding. This means uncertainty remains over how judges will approach similar cases.

Key takeaways 

Following this judgment, we would emphasise the importance of landlords serving accurate GSCs to avoid any procedural defects giving rise to a potential defence. Even if a procedural defect is noted, all hope is not lost, as this can seemingly be remedied provided the amended GSC is served on the tenant(s) before service of the S.21 Notice.

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