I believe you are talking about business insurance that every business should have. It includes but not limited to: Content (fixtures, equipments,inventories, every hard assets in your business, which you estimate the value, and this part cost the most in premium), Loss of Earning (say your building burned or damaged that you can not operate business and lost of your income, including your rent payment to your landlord. which you have to proof by your book), Auto and Liability (damage cost by you in the course of do business such as sign fall down, burnt you client's building, usually in the 1 mil or 2 mil range are pretty reasonable).
when you bid the install job for your client (say a small multi-location business), they might not inquire about your insurance, it is up to us to know that all Malls or shopping centers require a certificate of insurance name them as "additionally insured" with liability cover for a certain amount, in order to enter and working on their property.
It takes time to secure this coverage and paperwork if you don't already have this business insurance. Your choice will be sub to local sign company already qualified by that insurance requirement.
If you have business insurance policy, simply ask them to increase the liability coverage, and charge your client for the added cost.
Such is one of the joy to be in business.
