In line with the UK`s implementation plan (July 2020), a control system for goods entering From Great Britain into Northern Ireland requires three types of electronic documents, as described in an eleven-page document.  In 1922, the Land of Bavaria of Ireland[a] formally separated from the United Kingdom as an autonomous domination, in accordance with the terms of the Anglo-Irish Treaty, and prepared the conditions for full national independence, while Northern Ireland remained a member of the United Kingdom. As a result, the dividing line between these two parts of the island became an international border. Cross-border trade in goods and services is subject to different tax and customs regimes and a customs office infrastructure has been set up at designated border crossing points. All traffic has been checked by the jurisdiction into which it entered. This could result in complete searches with delay and inconvenience. In 1922, the United Kingdom and the newly created Irish Free State concluded a Common Travel Area (CTA) Agreement. This gave British and Irish citizens the right to travel, live and work in both jurisdictions. Passport controls are not used to travel between them. The rules of free movement that flow from EU membership replaced it to some extent, but the parties kept their bilateral agreement alive even though it had no contractual status.
In 2011, the UK and Irish governments informally agreed to continue their joint controls when nationals of non-EEA countries enter the CTT.  During the negotiations on the Withdrawal Agreement, some claimed that a hard border between NI and the Republic of Ireland would violate the Good Friday Agreement. . . .