The Legal Software Suppliers Association (LSSA) has published guidance for law firms and other users of legal software considering or undertaking a Data Conversion from one system to another. It details how the Data Conversion processes may vary, what should be expected of the new system supplier and the responsibilities of the current system supplier. The full text of the guidance can be seen here. The necessity for planning, and then the processes required to effect the conversion, are described in this paper, which would be very useful for any firm planning to change from one supplier to another.