1120s

Form 1120S is the tax return used to report income, losses, and dividends that are then passed-through to the S Corporation shareholders. The Schedule K-1 is part of the Form 1120S that identifies the percentage of share owned, profits, losses, and distributions for the tax year and must be prepared for anyone holding interest in the company. Note that it is possible for an S Corporation to have only one shareholder. 

You are considered an S Corporation If you have filed Form 2553 at any time during the year and the IRS has accepted the election. It is possible to file Form 2553 with the tax return (1120S​​​​​​​) and make the designation at time of filing. The IRS uses the ownership percentage to designate how much profit or loss should be assigned to the individual shareholders.

There are significant advantages and some downsides to choosing to be an S Corporation. S Corporation are subject to many of the same rules that C Corporations must follow, though there are significant tax benefits to being an S Corporation over a C Corporation, Partnership, or Sole-Proprietorship.