For calendar-year, file on or before April 15 (Form 1041 U.S. Income Tax Return for Estates and Trusts and Schedule K-1 Beneficiary’s Share of Income, Deductions, Credits, etc.).
For fiscal year, file by the 15th day of the fourth month following the tax year close (Form 1041).
If the due date falls on a Saturday, Sunday, or legal holiday, you the due date is the next business day.
If more time is needed to file the estate or trust return, use IRS Form 7004, Application for Automatic Extension of Time To File Certain Business Income Tax, Information, and Other Returns, to apply for an automatic 5 1/2-month extension. See the FAQ for details.
Definition of Fiscal year: 12 consecutive months ending on the last day of any month except December. A 52-53-week tax year is a fiscal tax year that varies from 52 to 53 weeks but does not have to end on the last day of a month.