Part I taxes on the organization. File Form 4720 by the

due date (not including extensions) for filing the organization's Form 990-PF, Form 990, Form 990-EZ, or Form 5227. If you aren't required to file any of these forms, file Form 4720 by the 15th day of the 5th month after the organization's accounting period ends.

If the regular due date falls on a Saturday, Sunday, or legal holiday, file by the next business day.

Affiliated group member. See section 4911(f) and the instructions for Schedule G, later, for definition of “affiliated group.” For the members of an affiliated group of organizations that have different tax years, and who are filing Form 4720 to report tax under section 4911, the tax year of the affiliated group is the calendar year, unless all members of the group elect under Regulations section 56.4911-7(e)(5) to make a member's year the group's tax year.