Under the Gas Safety (Installation and Use) Regulations 1998, landlords are legally obliged to ensure that all gas installations and appliances are adequately maintained and are safe to use. Landlords must instruct a Gas Safe registered contractor to check installations and appliances annually.
As part of this check, the contractor should provide a Gas Safety Record (GSR), a copy of which must be given to the tenants at both the start of their tenancy and annually thereafter. Ignoring these obligations is a criminal offence.
Full details can be found on legislation.gov.uk – The Gas Safety (installation and Use) Regulations 1998