Authorisation Code is the only identifier that is added to the gifts in RE and this is NOT unique. I have learned the hard way that Authorisation code can be recycled within two weeks i.e. given to different gifts from different donors on different days in a very short time frame.

Authorisation code is not present on failed payments so these have no id.

Without being able to match transaction in RE to BBMS tranactions it is very difficult to reconcile discrepancies e.g. when there is $30 more in BBMS than in the automatically created RE batches and there are 1900 transactions to check.