You join up with one or more other people to carry on a trade or business. Each partner uses their SSN or ITIN, and together they can either use surnames of the individual partners or come up with a business name. With a general partnership, you must file an annual information return to report the income, deductions, gains, and losses. Also - the partnership does not pay an income tax, but instead passes and profits or losses through to the partners who then include their share of the income or loss on their tax return.