Corporations file Schedule M-3 (Form 1120) to answer questions about their financial statements and reconcile financial statement net income (loss) Where to file your taxes for Form 1120-S ; A foreign country or U.S. possession.It provides supplemental federal income tax information for corporations. Report and pay FUTA tax if the corporation either: If you are an employer, you must file a quarterly Form 941 to report. It provides supplemen- tal federal income tax information for corporations. A few "must knows" for taxpayers to learn before starting the Free File Fillable Forms program.