GB / NI Backstop
The "invisible" backstop the DUP refuse^:
NI exports to GB would face no changes to current system
GB exports to NI trade with NI-only backstop exülained by Barnier
https://www.politico.eu/article/michel-barniers-zen-brexit/
"The EU proposes to carry out these checks in the least intrusive way possible.
For customs and VAT checks, we propose using the existing customs transit procedures to avoid doing checks at a physical border point.
Let me be more specific on this point,
because I think many of your companies are or could be concerned by these future relations.
Companies in the rest of the U.K. would fill in their customs declarations online and in advance when shipping bulk goods to Northern Ireland.
The only visible systematic checks between Northern Ireland and the rest of the U.K. would involve scanning the barcodes on the lorries or containers, which could be done on ferries or in transit ports."
Barnier noted that similar internal checks already take place as a matter of routine, with no political worries.
“These arrangements already exist within EU member states, in many of our countries,
in particular those with islands, for example between mainland Spain and the Canary Islands"