A wire transfer is simply a means of transferring money that has an electronic element. This can be a purely online transfer from one bank account to another, a system by which one person deposits cash at one location to be picked up by somebody in another location, or a combination of the two. The wire transfer number can refer either to the bank accounts used for the transaction, or the reference number used for the transfer itself.
The traditional form of wire transfer involves retail outlets. A customer will visit a branch of a wire transfer chain and hand over money plus the details of who is to pick it up. This person can then pick it up at any branch of the chain, most commonly in another country. Popular uses of this include people working in one country sending money to family back in their home country, and people wiring money to somebody who is traveling abroad and has got into financial difficulty.
In this context, the wire transfer number is usually a reference to the particular transaction, sometimes called a Money Transfer Control Number. In most cases, the person picking up the money will simply have to show adequate identification at the branch where they want to collect the money, and the wire transfer number will simply be a back-up check. In other cases, the number may have to be given by the person collecting the money as part of the verification process.
A wire transfer can also refer to a transfer between bank accounts. This is normally carried out online. In this situation, the wire transfer number can refer to several numbers. One would be the number of the bank account the money is going to. Another is the routing number of the bank used by the recipient of the cash, which sometimes also identifies the specific branch at which their account is held.
In the United States, this number is referred to as the American Banking Association routing number. In other countries, it may have a different name. For example, in the United Kingdom it is usually known as a sort code. Banks may also have a separate number specially for cross-border transfers. Transfers within the European Union use the International Bank Account Number, while international transfers using a system named SWIFT use a standardized code of eight letters to identify the bank, country and region, with another three numbers to identify the specific branch of office.