Abstract: An online store referral system is provided that includes an online store server comprising records of items for sale, a referral service server, separate from the online store server, and a primary referrer. A shopper computer system, of a shopper, is operative to receive from the primary referrer a link to an item for sale in the online store and to follow that link to make a purchase from the online store of the item for sale. The online store server is operative to inform the referral service server of a purchase of an item for sale following on from the link for that item being followed. The referral service server is operative to credit the primary referrer with a commission in respect of the sale of the item.