What is a digital link?
As part of Making Tax Digital legislation, HMRC says all technology that is used to record or calculate tax should be digitally linked—to be able to communicate with each other in a fully digital way, and at least one of the systems (if there are more than one) should be able to link with HMRC’s own computers.
All data transfers between software must take place digitally and HMRC points out that if you cut/copy and paste from one place to another—even within the same spreadsheet—then that does not constitute a digital link.