Proof of qualifications
Proof of insurance, public liability probably £2m, if doing EICR's then indemnity insurance
Current calibration certificate's for test instruments
Risk assessments
Safe working methods
A couple of jobs to take assessor to see (if still doing that with Covid19 around)
Questions tend to be fairly run of the mill stuff (max zs for circuits, Holes in joists, type of supply, you can refer to BS7671 if unsure on any question
Oversee you doing a bit of testing (make sure you get the safe isolation procedure correct)
In my book they like to see all the Bull_____ paperwork is in order
That's a kick start anyhow, I'm sure others will add to it !