A Schedule K-1 is a tax document used to report income, deductions, and credits from partnerships, S corporations, estates, and trusts. It provides detailed information about each partner's or shareholder's share of the entity's income, which is then reported on their individual tax returns. The form is typically issued annually and includes the taxpayer's name, identification number, and the specific amounts allocated to them. Recipients of a Schedule K-1 must use this information to accurately complete their tax filings, ensuring compliance with IRS regulations.