Which of the following needs to be filed by a business for partnerships and S-Corporations to report income?

In the context of partnerships and S-Corporations, Form 1065 is the appropriate choice because it is specifically designed for partnerships to report their income, deductions, gains, and losses. This form allows the IRS to evaluate how much income the partnership has generated and how it distributes that income among its partners. Partnerships themselves do not pay income tax; instead, they pass through their profits and losses to the individual partners, who then report those amounts on their personal tax returns.

S-Corporations file Form 1120S, which could lead to some confusion, but in the context of the question focusing on partnerships, Form 1065 is the correct filing instrument. Form 1040 is used by individual taxpayers for their personal income tax returns, and Form 1099 is used to report various types of income other than wages, salaries, and tips, but do not serve the purpose of reporting income for partnerships and S-Corporations specifically. Thus, the context provided reinforces that Form 1065 is the necessary document to be filed for reporting income related to partnerships.