Errors and omissions is a form of liability but whether you need additional coverage depends on the state issuing the policy, the type of policy, etc. Some states issue policies where they call it different things such as "Business malpractice, Quai-Tam, professional liability, etc. You have to shop around. One company I like that will give you several quotes from different places and you can pick the best one is NAPLIA. you can find them at
www.naplia.com Also if you have homeowners insurance you can check with them to see if you would qualify for any further discounts.