When given a report which adds new items several times a day but does not remove old items it becomes necessary to find a way to track each run of the report. A unique key is needed which could be an account number, or a transaction number if the same account number might appear multiple times. In some cases it may even be necessary to concatenate two fields to form a unique key such as account number + timestamp.
Once a unique key has been established you can add that to a list in work in progress. Items can be moved from in progress to a completed list either one at a time or in batches. From there filters can be added to check if the primary key appears on the completed or in progress. If it does not appear on either it should likely be added to in progress.