Which form is primarily used to report partnership income?

The most appropriate form for reporting partnership income is Form 1065. This form is specifically designed for partnerships to report their income, deductions, gains, losses, and other information. Partnerships are treated as pass-through entities for tax purposes, meaning that the income is not taxed at the partnership level; rather, it is passed through to the partners, who then report their share of the income on their personal tax returns.

Form 1065 includes information on the partnership's financial activities over the year and is also used to report each partner's share of the partnership income (on Schedule K-1), which is then used by the partners when filing their individual tax returns. This reporting structure helps ensure that partnership income is reported accurately and is taxed appropriately at the individual partner level.

The other forms mentioned serve different purposes: Form 1040 is for individual income tax returns; Form 1120 is used for corporate tax returns; and Form 1041 is designated for reporting income for estates and trusts. Therefore, they are not applicable for partnership income reporting.