During the inspection, the assessor will need to gather as much information as possible about the property to accurately produce an EPC. The information that is gathered by the assessor has to be evidenced for auditing purposes, this is usually done by taking photographs during inspection. If however the assessor is unable to gain evidence of any work that could affect the energy performance of the building, then documentary evidence such as a certificate would be required for the assessor to include the information into the assessment.

On the right is a list of information that if made available may help the assessor, remember that if the assessor cannot document any evidence for work that has been done (such as internal wall insulation) they cannot include it in their assessment, so a certificate for the completed work can be extremely beneficial for both you and the assessor.