From the Document: "After the 2016 referendum in which 52% of voters in the United Kingdom (UK) favored leaving the European Union (EU), 'Brexit' was originally scheduled to occur on March 29, 2019. In early 2019, however, Parliament repeatedly rejected the withdrawal agreement negotiated between Prime Minister Theresa May's government and the EU without supporting any alternative. In April 2019, the EU granted the UK an extension until October 31, 2019. [...] The dynamics of Brexit are likely to evolve in relation to pivotal events and deadlines in October 2019. Possible scenarios include a new withdrawal agreement, another extension, a no-deal Brexit, and an early general election in the UK."
CRS Report for Congress, R45944
Congressional Research Service: https://crsreports.congress.gov/