Electronic coupon system

System and method for automatically purchasing products and applying relevant coupons, for a customer. The system includes a customer knowledge database 104a which is used to determine a user purchase schedule 112b along with rules for substitutions of products 112c and budget constraints 112d. Electronic coupons are received at a coupon engine 114 from various sources and associated with an account of the user. Items are automatically purchased according to the purchase schedule, with product substitutions and coupons automatically being applied according to the rules. Where coupons will expire prior to a scheduled purchase date for a product, the product is purchased ahead of schedule if the budget constraints allow for the cost of this. The budget rules may specify how much to spend within a specific time limit. The automatic purchase of items may invoke automatic delivery of the purchases to a residence of the customer.