A method for managing stock so that a merchant who provides both on-line and in-person shopping may dependably advise an on-line shopper regarding availability of an item. An approximate quantity available of the item is determined, and then adjusted according to an estimate of the quantity of the item held before checkout by in-person shoppers. When the result is less than a threshold, corrective action is invoked. The corrective action may be prompting the on-line shopper to select an alternative item, asking the on-line shopper to submit an order immediately, monitoring the approximate quantity during the on-line shopping session and informing the on-line shopper if the approximate quantity falls below a second threshold, and instructing an in-house shopping assistant to reserve the item for the on-line shopper.