The Transaction Number (TA Nbr.) is an optional value which you can define.
The purpose of the transaction number is to allow you to create a unique identifier for a user and their transaction. This value is part of the result, allowing you to automate collation of the result and your internal process.
If a transaction number has been attributed, you can use it equally with the Ident-ID throughout the lifecycle of an ident process to, e.g., request updates or data.
We emphasize that this value be unique and not guessable.