A method and apparatus for encoding transactions for goods and services using an e-receipt is provided. A consumer and a merchant conduct a commercial transaction using a distributed data processing system. An electronic receipt is recorded on a removable storage medium at a first data processing system. The electronic receipt contains data concerning the commercial transaction. The removable storage medium is then read at a second data processing system. After validating the electronic receipt, another commercial transaction or another stage of the original commercial transaction may be performed. The electronic receipt may be validated for a warranty claim on goods or services subject to the purchase transaction, and the removable storage medium may be an optical card or a smart card, either of which is able to store thousands of e-receipts and other electronic documents related to a commercial transaction, with the integrity of each guaranteed through digital signature, digital certificate, etc.