Standing outside Number 10 on a wet Wednesday afternoon, the UK prime minister ended months of speculation and announced a general election would take place on 4 July.
It was expected the nation would go to the polls in the autumn and rules around general elections means some important bills will now not have time to pass through Parliament.
Here's what you need to know about the upcoming vote.
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How does a general election work?
A general election is held to elect Members of Parliament (MPs) to the House of Commons - one from each of the 650 constituencies in the UK.
On 4 July, registered voters will be allowed to cast one vote for their preferred candidate. Most will represent a political party, but there may also be independent candidates.
You can vote either at your local polling station between 7am and 10pm, by post, or by proxy - meaning someone votes on your behalf. You can also vote from abroad, if you’re a British citizen but not in the UK. Remember to bring a valid form of photo ID.
What happens to parliament when a general election is called?
Once a general election has been called, two big changes take place that affect the running of government.
1. Parliament shuts down
Following a general election announcement, a formal process takes place that effectively means Parliament will no longer formally exist. MPs then become candidates who campaign for re-election.
MPs continued to sit in the House of Commons until Parliament was 'prorogued' on Friday 24 May. Parliament will then be 'dissolved' on Thursday 30 May - 25 days before the vote takes place.
It meant the government only had two days to try to push through as much legislation as possible. Anything that wasn't completed by the end of the parliamentary session on 24 May will now not get onto the statute book.
Bills that passed include the Finance Bill, which includes the government's taxation plans as set out in the Spring Budget.
The Leasehold and Freehold Reform Bill, which aimed to improve homeownership for leaseholders in England and Wales, was also pushed through at the last minute. Although plans to remove ground rent for leaseholders or cap it at £250 were dropped.
The already passed through Parliament and was granted Royal Assent on Friday - the final step before becoming law. This bill aims to improve competition and protect consumers.
A key piece of legislation that was dropped is the Renters Reform Bill, which would have introduced changes to the private rental sector such as rent rise regulation. Plans to effectively ban smoking in future are also now shelved after the Tobacco and Vapes Bill failed to go through either.
2. Restrictions imposed
Previously called 'purdah', the 'pre-election period' involves placing restrictions on the government while MPs campaign for re-election.
Rules include stopping the party in power from using public money to fund their campaign and maintaining the impartiality of the civil service. These restrictions usually come into force once Parliament has been dissolved.
When will manifestos be launched?
During the campaign period before a general election, political parties publish documents called manifestos that set out what they will do should they win and form a government.
It's up to the individual parties when they unveil manifestos, but in the past the main parties have often announced theirs just a few weeks before the election.
It's very likely that political leaders from the main parties will also go head to head in a live televised debate. The format and timing of this are negotiated between political parties and broadcasters.
However, leaders are not obliged to take part. Theresa May, for example, refused to appear in any television debates during her general election campaign in 2017.
- Which? has published its own election manifesto, covering the key reforms we believe the next government should bring forward to improve consumer outcomes and boost economic growth. You can read it in full here.
What happens after a general election?
Under the 'first past the post' system, the candidate with the most votes is elected MP for their constituency.
After all the votes have been counted, the king will ask the leader of the political party with the most MPs to form a government. The second-biggest party will become the opposition.
A 'hung parliament' means no party has a majority, and the party with the most MPs may join forces with another party to form a coalition government. That happened in the 2010 general election when the Conservatives and Liberal Democrats were in power together.
Alternatively, the biggest party can run a minority government and rely on smaller parties to help them pass legislation.
The new parliament will be summoned to meet on 9 July, when the first business will be the election of the speaker and the swearing-in of members.
The state opening of Parliament will then take place on 17 July, followed by the King's Speech. This is when the new government announces its legislative agenda.
*This story has been updated since it was first published on 23 May. On 27 May we we updated which bills have passed and which have been shelved.
