New fusebox necessary?

Read the schedule of inspections and test results on an eic and you have your answer.

 

Just enter N/A for anything not applicable.

 

Because it was posted here, hence the question, what has it to do with a board change.

 

If the C3 doesn’t affect the safety of the consumer unit, you write it up in the box provided for that purpose on the Installation Certificate, that is what the box is for.

IET Model forms

https://electrical.theiet.org/bs-7671/model-forms/