An Energy Performance Certificate ( or EPC for short ) is the only legal requirement before marketing of a property commences, and made available at the earliest opportunity to potential buyers, and certainly before exchange.
There should also be a 'reasonable' expectation that the EPC will be made available within 28 days of the property first appearing on the market. This means when it is 'advertised' or otherwise 'promoted'. Failure to comply with this legislation may result in a penalty fine.
An EPC is valid for 10 years. You can market your home immediately once you have commissioned an Energy Performance Certificate. If you use an existing EPC nearing the end of its legal life (for example, 9 years and 11 months old), it will remain valid for as long as your home is continuously marketed. But if you temporarily pull your home off the market for more than 28 days, you will need to replace it if it's more than 10 years old when you resume marketing. A new EPC supercedes an older one.