Electronic transfer of money between bank accounts in Japan is called furikomi. You may need to do this when you buy an air ticket, buy something by mail-order, or apply to take a Japanese language test. Furikomi is normally done online, or at an ATM and there is usually a small handling fee. You will need to enter the payee’s bank name, branch name, and account number.
At an ATM, the account name (the person or company’s name) will appear on the screen after you enter the account number, so you can check it is correct. If you do not have an account at the bank whose ATM you are using, you have to enter your name, so that the payee knows who the payment came from. If you do have an account at that bank, the fee is slightly less. (Even if you do have an account at that bank, it may be necessary to do the furikomi as though you do not, so that you can enter your name or an invoice number etc.)
If you regularly need to transfer money to a certain account, you can register the account and get a special card (furikomi-ken) so that you do not have to enter the payee’s information each time. If the payee sends you a payment slip (furikomi yoshi) with barcodes on, you can pay it in cash at a convenience stores or post office counter, and you will not have to pay a handling fee.
There are several ways of transferring money at a post office, and the handling fees are usually less than at the bank.