Offer only valid for qualifying orders placed at a kiosk in-Shack, or for delivery or pick-up via the Shake Shack Mobile App or shakeshack.com, and fulfilled starting on Sunday, January 4th, and all Sundays subsequently after, through Sunday, June 28th (“Promotional Period”), at participating US Shake Shack locations (excluding airports, stadiums, arenas, travel plazas, and museums). Offer not valid for drive-thru orders or orders made through third-party delivery apps. Limit one (1) free Chicken Shack or Chicken Shack Lettuce Wrap per order. Max savings of $9.99. Order total must include a minimum of $10 worth of food or beverage products (including burgers, sandwiches, fries, chicken bites, hotdogs, drinks, shakes, frozen custard, poochinis, bag o’ bones), excluding the cost of the applicable Chicken Shack, gift card purchases and, any applicable taxes, delivery fees or other fees. Must add at least (1) Chicken Shack or Chicken Shack Lettuce Wrap to cart prior to checkout. Offer excludes Avocado Bacon Chicken and Chicken Bites. Offer excludes all paid add-ons such as avocado and bacon. Cannot be combined with any other offers or promotions. Must use promotional code ‘CHICKENSUNDAY' at checkout. Code is case sensitive. Offer code will only work in all caps.