The due dates for many tax returns were changed in an unlikely piece of legislation: the Surface Transportation and Veterans Health Care Choice Improvement Act of 2015, which was signed by the President on July 31, 2015.
For tax years starting after December 31, 2015 the automatic extension period for Form 5500 is increased from 2½ months to 3½ months. For calendar year plans, this means the extended due date will be November 15th instead of October 15th.
In addition, the Form 990 will now have a single automatic 6-month extension period beginning on the due date of the return without regard to extensions. The current first 90 day extension has been eliminated. A calendar year Form 990 filer with an original return due date of May 15th will now have an automatic extension until November 15th.