To sue a sole proprietor, you file against the person running the business, no matter what name he or she is using. Suppose that Sara Smith opens a dress shop called "The Dress Shop." Whom do you sue? The answer is Sara. To find out who "The Dress Shop" really is, check with the "assumed name" department in the clerks office.
To sue a partnership you should get the names of the partners. Under the law, each of the partners are responsible for the obligations of the partnership.
To sue a corporation, on the other hand, you file against the corporation. A corporation is a separate legal entity. To properly sue a corporation you should first contact the secretary of state and find out who the "agent for service" is so that you know who to serve with the papers. Call 1-800-252-1386 and ask for the business tax department to see if the business is listed. If it is, get the proper name of the business and the name of the registered agent. This is the person you will serve with your legal papers.
Once you have determined the proper legal entity to sue, make sure to get the
full name and address. A small error in spelling or an incorrect address could
cost you months when your papers cannot be served.