Schedule C is a tax form used by sole proprietors in the United States to report income and expenses from their business. It is part of the IRS Form 1040 and helps individuals calculate their net profit or loss, which is then included in their personal income tax return. On Schedule C, taxpayers list their business income, along with various deductible expenses such as supplies, advertising, and travel costs. This form is essential for self-employed individuals to ensure they accurately report their earnings and take advantage of available deductions, ultimately affecting their overall tax liability.