General election 2017 explained.

Theresa May announced a snap election in a surprise statement outside Downing Street last Tuesday, arguing that at a time of “enormous national significance” there should be unity in Westminster, but instead there was division. “The country is coming together, but Westminster is not,” the prime minister told the nation.

MPs voted overwhelmingly, by 522 votes to 13, to bring forward the election from its scheduled date of 2020. Here is everything you need to know about it.

What is a snap election?

Under the 2011 Fixed-term Parliaments Act, passed when David Cameron was prime minister, general elections in the UK are supposed to take place every five years on the first Thursday in May.

A snap election can be called for two reasons: if there is a vote of no confidence in the government or if MPs vote for an early election by a two-thirds majority.

When is polling day?

There is another vote on 4 May for county and unitary councillors and new “metro mayors”. These are local elections, not to be confused with the general election. It is unusual to have two big elections so close together, and it is expected that the local election result will be an indicator of what we can expect in June.

What time are polls open?

Polling stations will be open across the country from 7am to 10pm, and an exit poll at 10pm gives an indication of the result.

The counting begins after polls close and takes place through the night, with the first seat usually declared before midnight. If it is a strong victory for one party, the final result can be predictable by about 3am.

All those registered to vote will receive a poll card before the election which tells you when to vote and where your polling station is. If you forget or lose your poll card, you can still vote. At the polling station, staff will give you a ballot paper which lists the candidates you can vote for and you take this into a private booth.

How do you register to vote?

You must be registered to have a vote in the election.

You can register at gov.uk/register-to-vote, which requires you to answer 11 questions including your name, address, national insurance number and whether you want a postal vote. The deadline to register to vote is midnight on 22 May.

To qualify to register to vote you must be a British citizen, a qualifying Commonwealth citizen resident in the UK, or an EU citizen resident in the UK.

I’m a student. Where do I register to vote?

If you are a student you may be able to register to vote at both your home and term-time addresses, but remember that in a general election it is illegal to vote more than once.

How does postal voting work?

You can apply for a postal vote if you are away on the date of the election by filling out a form and sending it to your local authority. A postal vote can be sent to your home address or any other address that you provide, including overseas, but you must return your ballot paper so it arrives back by 10pm on polling day.

Alternatively, you can apply for a proxy vote, which means someone else will be allowed to cast your vote at the ballot for you. The person you appoint as your proxy must be over 18 and registered to vote.