The UK currently benefits from a number of EU trade agreements that have been negotiated with over 50 countries. EU agreements with a further 67 countries are currently under negotiation, including the US (known as the TTIP), Japan and India.
On leaving the EU (post Article 50) the UK would need to negotiate a trade deal with the EU (acting on behalf of the remaining 27 member states), and any non-EU country, that it wishes to trade with.
The UK will also need to update the terms of its World Trade Organisation (WTO) membership where the commitments have previously applied to the EU as a whole. This would mean negotiating and agreeing updated UK schedules of commitments with all 161 other WTO members. Until the UK’s schedule of commitments was updated, there would be a lack of clarity surrounding the UK’s rights to access WTO members’ markets, and the UK’s ability to enforce those rights.
Source: www.gov.uk ) (HM Treasury analysis: the immediate economic impact of leaving the EU page 28)
Source: ec.europa.eu (European Commission list of Free Trade Agreements)
Brexit Mythbuster 