Below is a list of Brexit-related legislation the government has promised to deliver, why it matters, and how much progress ministers have made towards turning it into law.

All the bills were originally intended to be passed during a specially extended two-year parliamentary session that started in June 2017.

The agreement of a transition deal with the EU lasting until Dec. 2020 has given the government more time to prepare for life after Brexit.

European Union (Withdrawal) Bill

This flagship piece of legislation will formally end Britain's membership of the EU and will also create the powers to allow ministers to transpose the current body of EU law into British law ahead of Brexit.

The bill has passed through the lower house of parliament, severely testing May's authority along the way, and is now being debated by the upper chamber - the House of Lords.

While the bill is unlikely to be blocked, the Lords are expected to defeat the government by voting in favor of several changes. That means it will return to the lower chamber, the House of Commons, for further debate before final approval.

The process is expected to be completed in the next couple of months, but is dependent on May being able to strike compromises with rebels in her party to secure their votes.

The longer it takes to approve the bill, the less time the government will have to complete the mammoth task of getting parliament to approve hundreds of technical changes to existing laws to make sure they function after Brexit.

Taxation (Cross-border Trade) Bill

More commonly know as the 'Customs Bill', this will create the framework for a new post-Brexit system of imposing duties on traded goods after Brexit.

The bill passed its first debate in the House of Commons in January, but the more rigorous stages of debate lie ahead. Those have not yet been scheduled as the government negotiates with rebel lawmakers who could derail it.

This bill, and the closely related Trade Bill, became a flashpoint earlier this year when pro-EU lawmakers from May's party launched a bid to require the government to remain in the EU's customs union. That is directly at odds with government policy to leave the customs union.

If backed by the main opposition Labour Party, the government could be defeated on a proposed amendment to the bill. But the rebels in her party have signaled they could back down without forcing the issue to a vote.

The bill must also pass the House of Lords to become law.

Trade Bill

The bill is focused on converting trade deals between the EU and third countries into bilateral deals with Britain. It creates a way to change domestic laws as needed to implement such deals. This is a technical bill and does not cover new trade policy.

Similar to the customs bill, it has passed the opening legislative stages, but the remaining parts of the process have not been scheduled yet amid attempts by some lawmakers to use it as a vehicle to keep Britain inside the customs union.

Immigration Bill

This bill will create a new immigration system, giving the government powers to restrict migrants' access to Britain where it sees fit once it is no longer bound by the EU's freedom of movement rules.

A desire to control migration into Britain was one of the main drivers of the vote to leave the EU in the 2016 referendum, and as such the government's new policy will be subject to intense scrutiny.

Before designing its policy, the government asked an independent body to report on the effect that EU migration has on the UK economy. An interim report in March found restricting migration was very likely to lead to lower output and employment growth.

Interior minister Amber Rudd said plans to publish formal legislation had been pushed back due to the agreement of a standstill transition period after Britain's official exit day of March 29, 2019.

Legislation is not expected until after the full report on the impact of migration has been published in September.

Fisheries Bill

This bill will govern foreign access to British fishing grounds, another highly emotive issue that has fueled anti-EU sentiment in coastal communities, where EU quotas have been blamed for the decline of Britain's fishing industry.

A decision to extend the status quo of EU quotas into the transition period immediately after Brexit provoked outrage among some in the industry, prompting a protest on the River Thames outside parliament.

The government has not published its long-term plan in either the form of a bill or a pre-legislative consultation document.

Agriculture Bill

This bill will set out Britain's farming and environment policy once it is no longer a member of the EU and subject to the bloc's Common Agricultural Policy (CAP).

Agriculture in Britain is heavily shaped by subsidies so the CAP replacement could have a big effect on what crops are grown, what animals are reared, and the methods used to do so.

The government has not published legislation on the subject yet, but has asked for views on a draft policy document.

Nuclear Safeguards Bill

This is the legislation that will allow for the replacement of the system of nuclear safeguards provided by Euratom, the European nuclear energy community which regulates nuclear material use in member states.

The bill does not spell out details of the replacement system, but creates the regulatory powers needed to do so.

Britain's decision to withdraw from Euratom has been highly criticized by some lawmakers who say it is creating an unnecessary layer of regulation which could affect access to nuclear material.

The bill has passed through both houses of parliament and is awaiting one of the final stages of the legislative process, in which changes made by the upper house are either accepted by the lower house, or overturned. This has not been scheduled.

Sanctions and Anti-Money Laundering Bill

The bill will enable the government to impose sanctions at a national level rather than through the EU, and will also update policy on anti-money laundering. At the point of Britain's exit existing EU-level sanctions will continue to apply, but the new laws are needed to allow ministers to amend and add to them.

The legislation began in the upper chamber and was passed to the House of Commons for consideration. It has two further stages to pass in the Commons, and is likely to then need final agreement with the Lords before becoming law.

The bill is likely to undergo heavy scrutiny in its final stages as the government looks to make last-minute changes to toughen rules to impose sanctions in response to violation of human rights. Those changes were sparked by a nerve agent attack on a former Russian spy in Britain.

The next stage in the process has not been scheduled yet.