Installing a POS will provide a clean slate, no past transactional data will be available on the POS. Reinstalling the POS will refresh the application and retain the data. Before proceeding with either, determine which is to be accomplished (always take a backup first, though).
Note: If the POS is "Installed" instead of "Reinstalled", transaction numbers will start back with 1 and be a duplicate for the register ID. The CAS will not recognize the additional sales as it sees them as already in the system (same transaction number).
This scenario may be reported by the merchant as transactions not showing up, as the transaction numbers will have already been used and the system will disregard the duplicate numbers.