An interbank transfer is a movement of money from an account at one bank to an account at a different bank. Because the two banks keep separate ledgers, the payment cannot be completed by one institution alone: the instruction has to travel through a shared system, and the banks must settle the amount between themselves. This distinguishes it from an intrabank or book transfer, one of the on-us transactions in which both accounts sit at the same bank and the money moves by a simple ledger entry.
Domestic interbank transfers run over national systems: an automated clearing house for batch payments, an instant payment scheme for small real-time payments, and a real-time gross settlement system for large or urgent ones. Final settlement normally takes place across accounts the banks hold at the central bank. Where no common system exists, as with most cross-border payments, the banks rely on a correspondent bank.