https://www.investopedia.com/terms/c/correspondent-bank.asp
How a Correspondent Bank Works
Correspondent banks are third-party banks. They act as middlemen between different financial institutions. As such, they provide Treasury services between sending and receiving banks, especially those in different countries—such as:
funds transfer
settlement
check clearing
wire transfers
currency exchange
Correspondent banks may also act as agents to process local transactions for clients when they are traveling abroad. At the local level, correspondent banks may accept deposits, process documentation, and serve as funds transfer agents.
A correspondent bank must act as the middleman when sending and receiving banks don't have agreements in place for wire transfers.
The accounts held between correspondent banks and the banks for which they provide services are referred to as nostro and vostro accounts. An account held by one bank for another is referred to by the holding bank as a nostro account or our account on your books. The same account is referred to as a vostro account—your account but on our books—by the counterparty bank. Generally speaking, both banks in a correspondent relationship hold accounts for one another for the purpose of tracking debits and credits between the parties.
Correspondent banks are a pivotal part of the financial industry as they provide a way for domestic banks to operate when it isn't feasible for them to open up branches in a different location—especially in a foreign country. For instance, a small domestic bank with clients in different countries can partner with a correspondent bank in order to meet the needs of its client internationally. Doing so also gives them access to the foreign financial market. The correspondent bank will, therefore, charge a fee for this service, which is usually passed off from the domestic bank to the customer.
KEY TAKEAWAYS
A correspondent bank is an authorized financial institution that provides services on behalf of another financial institution.
Correspondent bank services may include funds transfer, settlement, check clearing, and wire transfers.
The accounts held between correspondent banks and the banks to which they are providing services are referred to as nostro and vostro accounts.
Domestic banks can serve their international clients and gain access to foreign financial markets by using correspondent banks rather than setting up branches overseas.
Special Considerations
International wire transfers often occur between banks that do not have an established financial relationship. For example, a bank in San Francisco that receives instructions to wire funds to a bank in Japan cannot wire funds directly without a working relationship with the receiving bank.
Most international wire transfers are executed through the Society for Worldwide Interbank Financial Telecommunication (SWIFT) network. Knowing there is not a working relationship with the destination bank, the originating bank can search the SWIFT network for a correspondent bank that has arrangements with both banks. Upon finding a correspondent bank having arrangements with both sides of the transfer, the originating bank sends the transferred funds to its nostro account held at the correspondent bank.
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Using the example above, the correspondent bank deducts its transfer fee, usually between $0 and $50, and transfers the funds to the receiving bank in Japan. In transactions such as this, the correspondent bank adds value in two ways. It alleviates the need for the domestic bank to establish a physical presence abroad and saves the work of setting up direct arrangements with other financial institutions around the world.