After 11 pm GMT on 31 January 2020 the UK will no longer be a member state of the European Union.
There will then be a formal transition period which is currently scheduled to end on 31 December 2020.
Existing trade and tax rules for UK based businesses will not change in the transition period – the country is still effectively in the customs union and single market - so there is no immediate impact in the usage of Accounting and its API.
The next important deadline is 1 July 2020. If the UK wants to extend the transition period it must request it before this date and can extend by either one or two years (subject to approval). If it doesn’t, then we are potentially back into a countdown to no-deal Brexit on 31 December 2020.
If your application allows cross-border trading between the United Kingdom and the countries of the EU (you make use of sales or purchase invoices and credit notes and have not implemented any restrictions) then please check back regularly for alerts about upcoming changes in Accounting and the API.