When is IRS form 1065 due?

Form 1065 for domestic partnerships is due on the 15th day of the fourth month following the end of the partnership's tax year, according to the IRS. The due date is extended to the following business day if April 15 falls on a Saturday, Sunday or legal holiday.

Partnerships that keep their records and books outside the United States and Puerto Rico may add two additional months to the due date, says the IRS. All partnerships are eligible for an automatic five-month extension to the original due date by filing Form 7004. If a partnership terminates, its tax year ends on the date of termination.