The UK’s departure from the EU – BREXIT – took effect on 31 January 2020 under the terms of the Withdrawal Agreement agreed with the EU in October 2019. As a consequence, the UK has left the political institutions of the EU and entered a transition period. During this transition period (until 31 December 2020), EU regulations will in principle continue to apply in the UK. In the course of the next months the UK government and the EU will negotiate a comprehensive trade deal.
The BREXIT may have an impact on the treaty clearance for payments between Switzerland and the UK and puts treaty claims at risk based on the Swiss-US DTT:
Payments from the UK to Switzerland / from Switzerland to UK: replace 823C with 823B