Which tax form must be filed by a single-member LLC that is treated as a sole proprietorship?

A single-member LLC that is treated as a sole proprietorship is required to file Form 1040, Schedule C to report its income and expenses. This is because the IRS disregards the LLC as a separate entity for tax purposes, meaning that the business income is reported on the owner's personal income tax return.

Schedule C allows the owner to detail their business income and expenditures, which then flows through to Form 1040, where the net earnings are taxed as personal income. This streamlined reporting simplifies the tax process for individual owners of these types of entities, as they avoid the complexity of corporate taxation.

In contrast, other forms listed are applicable to different types of businesses or situations. Form 1065 is used for partnerships, Form 1120 is for C corporations, and Form 941 is related to employment taxes, making them irrelevant for a single-member LLC classified as a sole proprietorship. Thus, the requirement to file Schedule C underlines the simplicity and direct taxation approach for individual business owners.