A Certificate of Conformity (COC), also known as a gas compliance certificate, is required by law for all permanent liquid gas installations in your house and must be obtained from an authorised person or an approved inspection authority, which confirms that it is safe according to the applicable standards. Examples of gas installations that require this certificate include gas fire places or gas hobs, as well as gas hot water systems, etc.
There is no set period for the validity of the COC, but according to the Pressure Equipment Regulations of 2009 an authorised person shall issue a COC after a gas installation, modification, or alteration of the installation and where there is a change of user or ownership. There is thus a duty on a homeowner to acquire a COC when the gas appliance is installed, changed or altered and when the property is sold. So whenever the property is sold a new certificate must be obtained, regardless of how old the existing one may be.
The responsibility for obtaining this certificate falls to the Seller, unless the parties contractually agree that the Purchaser will obtain the certificate. Importantly, though, you cannot waive this requirement or contract to obtain it, as non-compliance is a criminal offence.
In your case, the COC is therefore required, and depending on your sale agreement, you, as the seller are probably responsible for obtaining such
