If the client has you covered under their insurance policy, it may be a good idea to request a copy. However, this should not relieve you of the need to carry your own insurance. Not all clients are going to incude you in their policy, and in those cases in which they do include you the amount of coverage may not be enough. If you were named as a defendant in a negligence (errors and omissions) suit, and were insured by both your own insurance carrier and your client's, the two insurers would adjust the claim between them if you lost the suit.