Hello @rafael_sahagun,
The discrepancy between transactions in Adobe Analytics and your backend system could stem from several issues, most notably duplicate or reused transaction IDs as you've seen, some IDs appear months apart, which can inflate AA's transaction count if not properly deduplicated.
Additionally, AA tracks data client-side, so transactions may be recorded if the purchase confirmation page is triggered before payment is completed or if users abandon the process after the beacon fires, while the backend only logs finalized orders. Test orders, bot activity, or tracking from development environments can also inflate AA numbers if not excluded.
Lastly, delayed or batched hits from apps or unstable connections can cause timestamp mismatches, making it appear that the same transaction occurred on multiple dates, further complicating reconciliation.
So, I would do all the above checks to narrow down on the issue.