You are legally obliged to have certain insurance policies in place for your business, depending on the nature of its activities. This could include motor insurance if you have company vehicles, employers' liability insurance if you have staff, professional indemnity insurance if you sell knowledge or skills to cover you in the event of a negligence claim and public liability insurance if you deal with the public.
In addition, it would be sensible to ensure your premises, stock and equipment against fire, flood and theft. You may also want to consider insuring your own health and that of your staff.
If your business employs people and therefore has employers' liability insurance, it must display the certificate in the workplace.