You can enter a valid promo code on the right side of the shipping/payment details page on our website. If you use Apple Pay to checkout you bypass the screen for entering the promo code (all your details are already in the app) and you will need to manually enter your shipping details then apply the promo code after selecting "Continue to Shipping.” Please note that our promo codes are valid both online and in shop, cannot be combined with other promotions or discounts, are not valid on previous orders or treatments and are valid on in stock items only.  See a screenshot of the promo code input here.