# Do I need a CP12 as a landlord in Hertfordshire or London?

*The Datum team · Heating, cooling & plumbing engineers · Datum · updated 2026-10-19 · Landlords*

Yes. If you let a property with any gas appliance, flue or pipework, the law requires an annual Landlord Gas Safety Record — the CP12 — carried out by a Gas Safe registered engineer. You must give tenants a copy within 28 days of the check (or before they move in), and keep records for at least 2 years. Good condition is no exemption, and the HSE says breaking the regulations could mean a substantial fine and/or a custodial sentence.

## What is a CP12, and what does the check cover?

A CP12 is the Landlord Gas Safety Record, the annual certificate a Gas Safe registered engineer issues after checking every gas appliance, flue and pipework you supply in a rented property. Under the regulations the engineer must examine the effectiveness of the flue, the supply of combustion air, the appliance's operating pressure or heat input, and that it operates safely.

Appliances the tenant owns aren't yours to certify, but the pipework serving them is.

## The renewal window worth knowing

You can renew a CP12 up to two months before its expiry and keep the original renewal date — so there's no reason to run it to the wire. We track expiry dates across your properties and book the renewals before you'd have thought to chase them.

## Portfolios

One number for every property: checks scheduled, certificates delivered digitally, reminders before each renewal, and a tidy audit trail if anyone ever asks. That's the whole point — compliance that runs itself.

> The renewal window is the most under-used rule in lettings — renew up to two months early and you keep your original date. There is never a reason to run it to the wire.
>
> — The Datum team, Heating, cooling & plumbing engineers

## Related questions

### How much does a CP12 cost?

It varies with appliance count and location — we price it fixed, in advance, and discount multi-property portfolios. Combining it with the annual boiler service in one visit is usually the cheapest route.

### What happens if I don't have one?

It's a legal requirement under the Gas Safety (Installation and Use) Regulations 1998. The HSE says breaking them could result in a substantial fine and/or a custodial sentence. Check your landlord insurance policy too.

### Can the same visit include a boiler service?

Yes — and it should. The CP12 is an inspection, not a service; doing both together saves a call-out and keeps the boiler warranty valid.

## Sources & verification

- [HSE — Gas safety: landlords and letting agents (check up to 2 months before the deadline and keep the original date; copy to tenants within 28 days; keep the record 2 years; breaches "could result in a substantial fine and/or a custodial sentence"; accessed 19 Oct 2026)](https://www.hse.gov.uk/gas/domestic/faqlandlord.htm)
- [HSE — Gas safety check records and what to keep (at least two years, or until two further checks if you use the early-check flexibility; new tenants get a copy before they move in; accessed 19 Oct 2026)](https://www.hse.gov.uk/gas/landlords/gassaferecord.htm)
- [Gas Safety (Installation and Use) Regulations 1998, regulation 36 (12-month checks; copy to existing tenants within 28 days of the check; accessed 19 Oct 2026)](https://www.legislation.gov.uk/uksi/1998/2451/regulation/36)
- [Gas Safety (Installation and Use) Regulations 1998, regulation 26(9) (after work on a gas appliance the engineer must examine the effectiveness of any flue, the supply of combustion air, its operating pressure or heat input (or combustion performance where that is not reasonably practicable) and its safe operation; accessed 19 Oct 2026)](https://www.legislation.gov.uk/uksi/1998/2451/regulation/26)

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Canonical page: https://www.datumclimate.co.uk/guides/cp12-landlord-guide