The Data Remover program was written primarily to remove old no longer active customers from the customer list (for those users reaching the maximum number allowed) but in can be used to remove other list names (items, vendors etc.) and also transactions.
In QuickBooks it's difficult to identify (at least programmatically) which customers have had recent activity and which haven't. After you identify the inactive ones, you can only delete them by merging them or starting a new file without them. The Intuit Software Development Kit (SDK) will not allow us to merge customers programmatically, so starting a new file is the only automated option left.
When using the Data Transfer Utility to start a new file, you can limit the transfer of customers to the new file to just those not marked as inactive but most users don't mark these old customers as inactive. You can also limit the customers transferred to the new file to just those created/modified after a certain date but typically this process omits a few customers that you need and you get missing parent rejects on customer imports and missing customer rejects on transactions. So we needed a better method of trimming the customer list.
Since QuickBooks will reject any attempt to remove a customer (or any list name) that is linked to a transaction, we decided to use that feature to in essence identify active customers (i.e. those with transactions). With the Data Remover you can start a new file, transfer all the customers to the new file and enter the beginning balances (and a few weeks or months of transactions if you want to). This leaves a lot of old customers in the new file who are not linked to any transaction and when you run the Data Remover, QuickBooks allows these customers to be removed but rejects the Data Removers attempts to delete customers who are tied to transactions (i.e. active customers).