insurance slip

I have a small office cleaning business, my customers ask for proof that my car insurance?
Do you need proof of car insurance or just an insurance certificate of liability insurance to cover the cases of slips and falls, etc.?
I can not think of a reason which would allow your insurance. You are not using your car to clean their offices. However, if you do not have car insurance, you need to get to their own protection. You do not want to risk losing everything you've worked in a lawsuit if you have an accident. The responsibility is to protect against any damage he might do or cause in the course of their work. Obviously what we must do everything in his power not to cause any damage or leave a floor covered with soap and water, and bring someone to fall, but need to be protected in case something happens.
Slip and Fall? You Decide.