If you're running a business, you will have to:
insure your business premises
have employers' liability insurance if you employ people
You can find more information on employers' liability insurance on GOV.UK.
The type and amount of insurance cover your business needs will depend on a number of things, including the risks your business is exposed to.
Some types of businesss may also need professional indemnity insurance.
You may also need insurance to protect yourself and your business in case you or your key staff are unable to work.