Old Navy Military Mondays Discount = Extra 10% off In-Store! I may get paid for ads or purchases made through links in this post.April 8, 2012 By Heidi 1 Comment On the hunt for more Military Discounts?? Take advantage of the to Old Navy Military Mondays! Just show your military I.D. at checkout, and you’ll receive an Extra 10% off your entire purchase! See Also: BIG List of Military Discounts & Freebies!