This is similar to PAS 2060. It is published by the British Standards Institute, covering reporting of Scope 1 and 2, and if possible, Scope 3, emissions associated with a particular product, project, service or event. In general its harder to achieve than PAS 2060.
If your business produces a wide variety of products or projects of widely different specification this might be extremely challenging, especially if Scope 3 emissions are a big part of the overall scope. However, if your business offers a fairly standard set of services or products it becomes more practical. For example: a wedding package, a standard city-airport taxi ride, production of a laptop computer.
As with PAS 2060, statements of fossil fuel emissions can be validated by external organisations like Intsilo. Such certifications can then be used to help promote your product to your customers.