Legal Question in Business Law in California

You don't give much information to go on. Obviously, each named defendant must answer, or face having his/her/its default taken. Is your solely-owned business an artificial creation, such as a corporation or an LLC? In that case, it cannot represent itself and must retain an attorney. Filing a joint answer, on behalf of both defendants, is possible and is sometimes done, but the filing fee must be paid for each defendant, even if there is only one document filed. Personally, I'd prefer filing and serving a separate answer on behalf of each named defendant. Also, I'd recommend making sure the business is legally "up to snuff" at an early stage of the litigation, i.e. that its Franchise Tax Board and Secretary of State payments and filings are up-to-date (if any required) and/or that it has filed and published its fictitious business name statement (again, if required, which depends upon factors including type of business organization).

I suggest you point out the error to the plaintiff. Depending on the case, you may be able to demurrer if the defect is on the face of the complaint and it is not a limited civil case.