The filing deadline for calendar year partnerships and S corporations is March 15, 2017. These returns must be filed (e-filed or postmarked) by midnight (local time) on March 15, 2017. Fiscal year returns will be due the 15th day of the 3rd month following the year end. Both partnership and S corporation returns are allowed a six month extension, if needed. Payment must accompany the return or extension if there are taxes due. An extension of time to file does not extend the time to pay taxes that are due.