Systems and methods for effecting online financial transactions between individuals or between individuals and entities such as banks, merchants and other companies. Each user accesses a fund exchange server to establish an online account, which is used to transfer funds to and from other entities' online accounts. To fund an online account, funds can be transferred to the online account from a credit card account or from another online account. To withdraw funds, money can be transferred to a credit card account or other bank account. Any user may initiate a send money transaction or a request payment transaction with any other entity provided that entity has an e-mail address. For a send money transaction, the user sending money (payor) enters an amount of funds to be transferred and an e-mail address of the recipient of the funds (payee). The system sends an e-mail message to the payee at the address provided indicating that the amount of funds has been "received" on the payee's behalf. The payee must then either open an online account or identify an existing online account to complete the transaction. For a request money transaction, a user enters an amount of funds owed and an e-mail address for the recipient of the payment request (payor), and the system sends a payment request to the payor via e-mail at the provided address. If the payor accepts the payment request, the payor identifies an online account from which to transfer funds to the payee (initiator of the payment request). If the payor does not have an online account established, the payor must sign up for an online account and provide a credit card number to fund the online account. Thereafter, the amount of funds are transferred to the payee and the system sends an e-mail notification to the payee indicating that the funds have been "received" on the payee's behalf. In both cases, to complete a transaction, the payee must direct the received funds to an online account, for example, by providing an online account number and/or other identifying information such as a password. The payor may cancel the transaction at any time until the payee directs the received funds to an online account.