It is a special set of numbers that defines each transaction, with the help of it the bank workers can identify in the bank system the purchase that was made by the customer. It is always unique that means that there are no transaction IDs that are the same. This transaction key is usually generated after the system defines it as a successful one. The key normally consists of numbers and letters (a 12-digit code).
If the customer wants to search for a particular payment, the transaction ID is needed. The ID is also very important if the client has an intention to ask for a refund. This ID can be found in the top right corner. This one also can be used to authenticate the holder of the card before reporting the data about the payments of a particular customer.
Here are some examples:
Could you please mention the transaction ID, so we can check the payment situation?
I should find the transaction ID first in order to get a refund.