Aztec
I used to be involved with this when working for a building company and haven't been involved for a couple of years and used to consist of the following:-
You have to complete a questionnaire and return with all your health & safety stuff. i f you have less than 5 employees you shouldn't have to provide much info but they will probably want risk assessments, method statements, details of any safety courses or qualifications that you hold and insurance details. If you employ more than 5 people you will have to send copies of your H&S policy etc etc
Once you are acredited your details are available for anyone whose looking for a 'safe' contractor to contact you.
Hope this helps
Pippin