On 31 January 2020, the UK officially left the EU, thereby starting the so-called “transition period” (see “Brexit – not an end but a new beginning”). During this period, ACER claims that EU rules will continue to apply, including the Regulation on wholesale energy market integrity and transparency (REMIT). Accordingly, market participants from the UK will not have to register in another EU Member State during the transition period and will still be required to report REMIT data to ACER. In the course of 2020, ACER will continue “business as usual” by monitoring the application of EU law in the UK and following developments closely to best anticipate the end of the transition period. Since there is currently no indication that the transition period will be extended, ACER states that “as of January 2021 UK market participants willing to continue entering into transactions or placing orders to trade in the EU’s wholesale energy markets will have to register in one of the remaining 27 EU Member States”.