We use various methods for preventing duplicates. Cleared (booked) transactions should not be an issue, as each transaction is assigned a unique identifier by our provider and your bank.
Pending transactions can be tricky however, as they do not have a reliable unique identifier. For this reason we have implemented our own duplicate checks, based on the complete transaction data. This works well for most banks, but there might be some banks that offer very little transaction data. In these cases, detecting duplicates can be difficult.
If you are receiving duplicates, you can try to apply any of the following settings in your source:
Disable "Sync pending transactions"
Enable "Match with existing YNAB transactions"
Enable "Strict duplicate check"
You can find these settings under Source > Settings.
If you have tried the above and are still receiving duplicates, do not hesitate to contact us by chat or email.