With Statement Direct on automated download, the transactions will be extracted into NetSuite one day later depending on your time zone. First the banking day needs to close out and then the script runs at a set time to bring in those transactions. The script can be modified to change the time that it imports in the statement.
Duplicates should not happen. Each bank statement line has a unique sequence number. It only downloads lines with different sequence numbers from existing lines. You can delete transactions from Statement Line > ABR Bank Statement Line List or ABR Bank Statement > View > Edit line.
