Schedule K-1 A Schedule K-1 is a document used to describe incomes, losses, and dividends of a business’s partners or an S corporation’s shareholders. As you can see, Schedule K-1 is complicated, and it may take an expert to calculate each owner’s share of the business profit or less. Return of Partnership Income is a tax document issued by the IRS used to declare the profits, losses, deductions, and credits of a business partnership. A simple tax return is Form only, without schedules 1, 2, or 3. Schedule K-1 reporting The Schedule K-1 is slightly different depending on whether it comes from a trust, partnership or S corporation.