The Prime Minister will detail her 12-point plan on negotiating Britain's exit from the European Union during a key speech on Tuesday morning.
But what are the key issues that businesses, politicians and voters would like to see more clarity on?
- Access to the single market
The Prime Minister has said she wants the "best possible deal in trade with and operating within the European Union", but her insistence on gaining full control of immigration appears to rule out the UK staying in the trade bloc.
The European Union insist that free movement of people is a non-negotiable condition of membership.
- Membership of the customs union
Theresa May's aim of striking a deal with the United States and New Zealand appears to rule Britain out of staying in the tariff-free area.
International Trade Secretary Liam Fox has suggested the UK could still remain a partial member, whereas Chancellor Philip Hammond remains unsure.
- Payments to the EU
David Davis, the Secretary of State for Exiting the European Union, has suggested the UK could keep paying money to Brussels after it leaves the EU in order to remain in the single market.
However this appears unlikely given the Prime Minster is expected to announce she will not settle for a "half-in, half-out" policy.
The idea will also irk Tory backbenchers and Eurosceptics in Ukip.
- Brexit timetable
When will the UK leave the European Union?
The European Union's lead Brexit official, Michel Barnier, has said Britain needs to reach a deal by spring 2019.
However it is unsure whether Mrs May accepts this timescale.
- Transition period
Businesses have appealed for the Prime Minister to avoid a "cliff-edge" scenario - when Britain leaves the European Union - and instead offer a transition period.
Mrs May is keen on the idea, but is wary that it must not be a way of "putting off actually leaving the EU".
- Rights of EU citizens
Ever since Britain voted to leave the EU on June 23, Mrs May has been under pressure to guarantee the rights of European Union nationals already in the UK.
The Prime Minster has said she wants and expects to be able to do this, but wants assurances Britons living abroad are given the same guarantees.
- Workers' rights
Labour is concerned there will be a watering down of EU guaranteed protection for workers, as the country enters a more competitive global market.
Jeremy Corybn will be looking for assurances that Briton's rights will be maintained.