October 1, 2015
Chapters must file their annual tax return for the last AMBUCS year (June 1 - May 31). Chapters with gross receipts of less than $50,000 can file using the 990-N postcard. http://epostcard.form990.org/
Those chapters with receipts of more than $50,000 must file using form 990 or 990-EZ.
The deadline is October 15th.