Theresa May first proposed a transition, or implementation, period in her Florence speech in September last year. She said that she thought it should last “around two years”, but when they set out their negotiating guidelines in January, the commission’s negotiator, Michel Barnier, introduced a December 2020 deadline. A shorter transition period avoids complexities over a continuing UK contribution to EU finances in return for access to the single market and the customs union, which continue during the transition period. The new EU accounting period, called the multiannual financial framework, ends at the end of 2020.