Sole Proprietorship- A business that legally has no separate existence from its owner. Income and losses are taxed on the individual's personal income tax return. The sole proprietorship is the simplest business form under which one can operate a business. The sole proprietorship is not a legal entity. It simply refers to a person who owns the business and is personally responsible for its debts. A sole proprietorship can operate under the name of its owner or it can do business under a fictitious name, such as Nancy's Nail Salon. The fictitious name is simply a trade name--it does not create a legal entity separate from the sole proprietor owner.