A business owned by a single person that is not a
corporation, a
limited liability company, or anything else. The sole proprietor who owns the proprietorship must list all
profits and
losses on his/her personal
tax return and does not file a separate return for the business. Additionally, the proprietor is personally responsible for all
losses and
debts the business incurs. Some small businesses begin as sole proprietorships and then become something else. Other sole proprietorships are part-time businesses that their owners operate on the side.