You won't need your legacy system for day-to-day use. You may, however, find it useful to keep your legacy system installed on one computer, at least until your financial bookkeeping is closed for the year.

Any financial transactions that started in your legacy system, must be completed in your legacy system. For example, if a patient comes in for a refund on a transaction that originated in your legacy system, you will need to process the refund in your legacy system.