Birchbox Coupon: Get FREE Discovery Kit With 6-Month Subscriptions! Last updated by Hello Subscription on September 8, 2018. Subscription Box Coupons & Deals / Birchbox Coupons Hello Subscription may earn compensation via links in this post. Read the full disclosure Save for Later Notification Birchbox is giving a FREE Discovery Kit when you get a 6-month Birchbox subscription! Just use the coupon code for the matching kit to get the deal. Valid for new subscribers only, and while supplies last.