Abstract: Transaction handling apparatus for effecting a transaction between a group of purchasers and a vendor. The transaction handling apparatus includes vendor apparatus running a vendor process which displays at least one user operable component associated with a product or service on offer. The transaction handling apparatus also includes server apparatus which stores purchase data comprising identification data identifying each of plural purchasers. The transaction handling apparatus also includes plural client processes and payment processing apparatus which receives payment in respect of each of the client processes and conveys the payments to the vendor in dependence on operation of the client processes. A payment received in respect of a client process forms a part of the price of the product or service. Operation by a user of the user operable component stores product data relating to the product or service, the stored product data being comprised in the purchase data.