surely your COC only cover the part of the installation which you fill in on in section 3 "description of installation covered by the this certificate" and not the entire installation and all additions done by other people...if you clearly state eg 5 plugs 2 light and 1 sub db what more could they ask for otherwise it becomes open book for all installation electricians to get NAILED... not that it will ever happen but rather be safe than sorry.