The Brexit deal agreed with EU leaders in December that the British parliament is voting on Tuesday is aimed at ensuring a smooth exit from the European Union on March 29.

Key provisions aim to avoid a hard border between EU member Ireland and the British province of Northern Ireland, protect citizens' rights and settle Britain's last bill.

The Irish issue proved to be the main hurdle in intense and bitter negotiations and is the key objection for hardliner Brexiteers who are planning to vote against the deal.

Following are the main points of the deal:

Irish 'backstop'

The deal outlines a “backstop” arrangement to prevent the return of border checks between Northern Ireland and Ireland if the sides fail to agree a free trade pact after a 21-month transition period.

In a bid to allay British concerns that Northern Ireland would be split from the rest of Britain, the two sides agreed to an EU-UK single customs territory.

Northern Ireland would follow EU single market rules on the movement of all products, including agricultural goods.

With the UK applying the EU's Customs Code in Northern Ireland, Northern Irish businesses would bring goods into the single market without restrictions.

The draft also stipulates that the Northern Irish economy retain unfettered access to the rest of the UK.

At London's request, Northern Ireland will apply all the rules of the single market for electricity.

In the single EU-UK customs territory, UK goods will enjoy tariff and quota free access to the remaining 27 EU countries.

EU diplomats had expressed fears British companies could manufacture products more cheaply if they dropped EU standards.

Both sides have given themselves until July 1, 2020 to outline a deal to replace the backstop. If one is not ready by then, they could extend the transition period by up to two years.

At any point after the transition period, either side can rule that the arrangement is no longer necessary, but they must take the decision together.

Transition period

During a transition period ending on December 31, 2020, EU law will apply to give national administrations and businesses time to prepare for new ties.

This means the UK will continue to participate in the EU Customs Union and the Single Market and little will change in practice for ordinary Britons and EU citizens.

It allows Britain continued market access to the remaining 27 EU countries but it must respect the rules on free movement of goods, capital, services and labour.

The British government will however lose the right to vote on any decisions taken by the 27 other member states, the European Commission and the European Parliament.

'Citizens rights'

The draft deal preserves the rights of the more than three million EU citizens living in Britain and the one million British citizens living in the EU.

EU and UK citizens, as well as their family members, can continue to live, work or study enjoying equal treatment to host nationals under the respective laws.

It covers all such citizens who arrive before the transition period ends.

They will maintain their right to healthcare, pensions and other social security benefits.

Brexit bill

Covering Britain's outstanding financial obligations to the bloc, it calls for a fair settlement for UK taxpayers that the British government estimates to be up to 39 billion (44 billion euros, $51 billion).

Dispute resolution

Disputes between businesses or other entities will be consulted on in a joint committee and, if no mutually agreed solution can be found, it will be resolved by an independent arbitration panel.

Gibraltar

With longstanding Spanish claims to Britain's neighbouring Mediterranean outcrop of Gibraltar, all sides sought to defuse any future tensions.

The deal provides for Spanish-British cooperation on citizens' rights, tobacco and other products, environment, police and customs matters.

It sets the basis for administrative cooperation for achieving full transparency in tax matters, fighting fraud, smuggling and money laundering.

British bases in Cyprus

The deal aims to ensure no disruption or loss of rights for the 11,000 Cypriot civilians living and working in the areas of the British sovereign military bases.

It aims to ensure that EU law will continue to apply in the base areas, including on taxation, goods, agriculture, fisheries and veterinary and phytosanitary rules.

Other points

It oversees the UK's withdrawal from Euratom, the EU treaty on nuclear energy and protects intellectual property, including trademarks as well as more than 3,000 EU geographical indications.

The latter cover regional brands such as Welsh lamb, Parma ham, Champagne, Bayerisches beer, Feta cheese, Tokaj wine,Vinagre de Jerez (Jerez vinegar).

Future ties

Separate from the divorce agreement, the two sides still have to negotiate their future relationship, particularly on trade — a process which could take years.