::I have seen this when working with journals like the general journal. If your batch has a No. Series assigned your journal lines will auto number based on the No. Series table. But if you switch to another journal batch which uses the same No. Series, you will start to get duplicate document numbers. The No. Series table is not update for that series until the journal is posted. You can click on Renumber Document Numbers prior to posting and then the system will go back to the update No. Series to grab unused numbers.