According to the Commission, negotiations need to be finalised by autumn 2018, to allow for orderly UK withdrawal by 29 March 2019, as a withdrawal deal requires the consent of the European Parliament and UK approval in accordance with its own procedures. The EU-27 and the UK could extend the deadline by common accord. The referral of a draft agreement to the CJEU remains a possibility, with the implications for the schedule difficult to predict.
On 13 July 2017, the UK government introduced in the UK Parliament the European Union (Withdrawal) Bill that would revoke, as from the withdrawal date, the 1972 European Communities Act, which gives effect to EU law in the UK, while transposing most existing EU law into UK law. The bill still faces scrutiny in the Parliament. A recently adopted amendment to the bill would prevent British ministers from using their powers to implement any exit deal agreed with the EU, before parliament has held a full vote on it. Another amendment relative to the precise UK withdrawal date will be voted on the 20th December. The UK government wants set in law the 29 March 2019 as the exit date, while some UK Members of Parliament argue this would make it difficult to extend the negotiation period should this be decided by the UK and the rest of EU Member States. The UK has also announced the withdrawal agreement will be directly implemented in domestic law, through the ‘withdrawal act and implementation bill’.