Tax Extension Filing Deadline. If, for one reason or another, you are unable to file your tax return by the April 17 tax deadline, you can file for an IRS tax extension. Note that the extension must be postmarked by the April 17 deadline also.When are extensions due for 1120s?
Tax Reporting for an S corporation. Form 1120S is due on the 15th day of the third month following the end of its tax year. For a calendar year, Form 1120S is due March 15th (or the next business day if the 15th falls on a Saturday, Sunday, or holiday). Form 7004 is used to file for an automatic 6-month extension.