Birchbox Sale: Save 20% on ALL Prepaid Subscriptions! LAST DAY! Posted by Hello Subscription on September 18, 2017. Subscription Box Coupons & Deals / Birchbox Coupons / Birchbox Man Coupons . The links in this post may be affiliate links. Read full disclosure Save for Later Notification Today’s the last day for this sale – Birchbox is offering 20% off 6- and 12-month Birchbox prepaid subscriptions and 6-month Birchbox Man subscriptions ! Just use code 20FORCAD! Valid on Birchbox & Birchbox Man.