When is Form 990 due? Form 990 is due on the 15th day of the 5th month following the end of the organization's taxable year. For organizations on a calendar year, the Form 990 is due on May 15th of the following year. Additional information Return due dates for exempt organizations annual return Extension of time to file exempt organization returns Interactive training Learn more about the benefits, limitations and expectations of tax-exempt organizations by attending 10 courses at the online Small to Mid-Size Tax Exempt Organization Workshop.