Basic Message Flow
The basic SWIFT message flow involves syntax validation and confirmation of receipt and acceptance.
When you send a message to the SWIFT network, SWIFT validates the syntax of the message. If the message is correct, SWIFT accepts the message, sends you an ACK, and attempts to deliver the message to the receiver. If the message does not comply with the standards, SWIFT rejects it and returns a NAK. The NAK contains an error code, which helps the sender identify the type of error and its location. The sender can then correct the message before resending it to SWIFT.
SWIFT delivers the message as soon as the receiver is logging in to the SWIFT network. The interface at the receiver's end automatically confirms the receipt and acceptance of the message by sending a UAK. When a UAK is received by SWIFT, the message is considered to be delivered. If the message received is corrupted, the interface of the receiver sends a UNK to SWIFT, and SWIFT attempts to redeliver the message.