When an invoice run is performed, all the invoices on that run will be put under a Batch Number.
this Batch Number is used when reprinting the entire Invoice run, and when exporting the Invoice Data to an external Accounts Package (e.g. Sage, Xero, Quickbooks)
When we open the Export invoices screen the LATEST batch should always show at the top of the grid (providing you have not altered the Grid order)