Form 990 for non-profit organizations with a December 31 year end are due May 15. An extension can be filed to give the non-profit more time to file. Generally, Form 990’s are due 5 months and 15 days after a non-profit organization’s year end. A complete list of non-profit year ends and due dates can be found here. If you aren’t sure which 990 your organization needs to file, a list and information for all Form 990s can be found here.