The next 2 sentences have force of law under regulation 3 of the Example Regulations 1995.

If a set of software programs, products or applications are used as functional compatible software there must be a digital link between these pieces of software. This digital link is required where the data to be included in any of the boxes of the Example Return has been prepared within a software program, product or application, and this data is then transferred to another program, product or application in order to submit the Example Return data to HMRC via the API platform.