We are so sorry to hear you forgot to add a promo code at checkout or did not select a promotion at checkout. We are unable to edit an order once it has been placed, as the packing slip is printed at our warehouse within moments of the order going through. This keeps our warehouse efficient and gets your order to you as quickly as possible. We're really sorry for any disappointment this may cause. We would suggest double checking the terms and conditions to see if this can be used on a future order.