That’s what #4 tried to say.
On an EICR, you list limitations, ie What doesnt get tested….
On an EIC, you list “extent of installation…” ie What does
And in the case of a new CU, it’s just the new CU….
Saying that, you may have performed a mini EICR just to check there was no underlying gremlins going to cause problems with RCDs etc.
If you are doing an EIC, that is an initial test of the work…. Work that you should have been part of, and you would know cable routes.
Example… you’re adding a spur or extending an rfc to a new socket right next to an existing one.
“Extent of installation” is simply the new bit of cable and socket you’ve put in. And whether rcd protection is in place for the new socket not necessarily the existing socket. (Although it’s much easier if the whole existing circuit is now rcd protected)