England and Wales
Since 1 April 2018, it is illegal to let out any residential property in England and Wales with an EPC rating of band F or G (the least efficient bands).
Since 1 April 2020, it is illegal to continue letting out residential property that doesn't have an EPC rating of band E or higher. This means that from 1 April 2020 all residential properties let out to tenants must have an EPC rating of E or higher.
From 1 October 2020, all new residential tenancies granted in Scotland must have an EPC rating of band E or higher. By 31 March 2022, all properties will need to have at least EPC band E.
From 1 April 2022, all new tenancies must have an EPC rating of at least D, and by 31 May 2025, all properties will be required to have an EPC rating of at least D.
In Scotland, the EPC must be displayed somewhere within the property (eg in the meter cupboard or next to the boiler).
For further information read Minimum Energy Efficiency Standards for residential properties.