Also known as IRS Form 1065, this IRS document is used by a partnership (e.g. an LLC or subchapter S-corporation) to report an individual's share of the partnership's income, deductions, credits, etc. If you are a shareholder in a subchapter S-corporation or have capital interests in an LLC partnership, you receive Schedule K-1 from the business and use the information reported in it on your tax return. For details, see the form's instructions.