For tax years beginning after January 1, 2016 (i.e. returns that will be filed in 2017), there are several important changes that have been made to the due dates of various returns.
The most significant change is that Partnership federal income tax returns (Form 1065 and the corresponding Schedule K-1s issued to the individual partners) will now be due March 15 instead of April 15th. This should actually make filing the individual partner’s 1040s easier, as the partners will have received their K-1s a month prior to their 1040 filing deadline. Previously it was often the case that the partnership did not file its return until April 15th, which meant that the individual partner’s themselves did not receive their Schedule K-1s on time to file their 1040 on a timely basis. This often meant that they were required to file extensions in order to complete their 1040.
Additionally, calendar year C Corporations federal income tax returns, Form 1120. will now be due on April 15th instead of on March 15th. For the due date for C Corporations with non-calendar fiscal year ends see the AICPA due dates summary chart link below.
There are also changes to the dates of various extension due dates for the Trust and Estate Form 1041, Exempt Organizations Form 990, as well as a change in the due date and the extension for the Foreign Bank and Financial Accounts Report filing of FinCEN report 114.
A summary of all of the changes can be found in the following AICPA chart.
Here is an article in the journal of accountancy which goes into greater detail on changes and the rational behind the changes.