Although BS7671 effectively says a certificate for each modified circuit it does not say every individual modified circuit must only have its own dedicated certificate.
If you provide two certificates where you have modified two circuits, as is totally in accordance with BS7671, and then realise that there is a lot of duplication on the forms and decide to combine the information that is duplicated into a single form and have the specific information for each circuit separately on the one form then this would also be compliant.
This is using the "based on the model certificate" statement and ensuring that you have provided all the required information in a clear and compliant format.
A couple of quickly prepared forms (delta comes out as ?, sorry) to demonstrate:
two forms (on one sheet)
vs one form for two circuits which looks better and saves paper (one less safety information page since I combined the two forms).
If you provide two certificates where you have modified two circuits, as is totally in accordance with BS7671, and then realise that there is a lot of duplication on the forms and decide to combine the information that is duplicated into a single form and have the specific information for each circuit separately on the one form then this would also be compliant.
This is using the "based on the model certificate" statement and ensuring that you have provided all the required information in a clear and compliant format.
A couple of quickly prepared forms (delta comes out as ?, sorry) to demonstrate:
two forms (on one sheet)
vs one form for two circuits which looks better and saves paper (one less safety information page since I combined the two forms).