A system and methods for conducting Internet based financial transactions between a client and a server. The client has a processor, a printer, a client authentication module, a module for issuing a transaction request, and a unique digital signature. The server has a network including a transaction server, a transaction database, a server authentication module, and a receipt generation module. An internet connection is used between the client and the server network. The transaction execution system includes authentication, wherein the client authentication module and the server authentication modules communicate via the internet connection and are authenticated to each other. A transaction module is included wherein, in response to the client and server being authenticated, the client issues a transaction request to the server and the transaction server, in response to a client transaction request, executes an electronic payment transaction at the server and records the transaction in the transaction database. The server receipt generation module, in response to an executed electronic payment, then generates a receipt and transmits the receipt to the client. The receipt includes the client digital signature and a data set uniquely identifying the executed transaction and is printable by the client printer. The printed receipt is an evidence of payment for the executed transaction. In addition, a third party seller having a processor and a database can be connected via a communication channel to the server, wherein the client further obtains a registration certificate representative of being a consumer registered with said third party seller. A third party credit facility also may be connected via a communication link to the server, for implementing credit card transactions. The transaction execution system may be to purchase an amount of postage, to purchase a ticket for air travel or to an entertainment complex or the like.