CNBC Explains

All you need to know about UK’s Brexit vote

What on earth is Brexit?

After years of infighting and debate, decision time over whether Britain will stay in the European Union (EU) is looming.

Prime Minister David Cameron got the ball rolling on Saturday when he announced the date for a referendum on June 23 after he clinched 11th-hour concessions from other EU leaders on how the U.K. and the rest of Europe will live and work together.

CNBC breaks down the arguments surrounding Britain's EU membership and outlines the potential political, economic and financial fallouts of a "Brexit."

‘Special status’: The EU’s concessions for Britain

U.K. Prime Minister David Cameron left Brussels on Friday, February 19, after marathon talks that yielded some concessions from EU leaders over how the U.K. stands In Europe.

The U.K. has long had a fractious relationship with the rest of E.U., claiming it is overly meddlesome. Some so-called euroskeptics claim that Brussels is encroaching on the U.K.'s sovereignty.

Following the announcement of Cameron's deal, the British media have zeroed-in on some key issues of the concessions: restrictions on state benefits for EU citizens and protection for Britain's financial sector.

The UK is now eligible to activate an emergency freeze on benefits for employed migrants, which would require residents to work for four years before they're eligible for full state financial aid like tax credits. Once triggered, those rules would be in place for seven years.

Those who can't find a job within six months will now be required to leave.

Meanwhile, EU citizens claiming child benefits for kids still living abroad would receive payments at a rate relative to the cost of living in their home country. Existing residents would see these restrictions phased in by 2020, but impact new migrants immediately.

Cameron also outlined a "safeguard" for British businesses that would ensure U.K. firms aren't discriminated against for being domiciled in a country that doesn't use the common currency, and said businesses wouldn't be forced to relocate their headquarters in order to trade in euros.

The basics: What? Who? When?

British Prime Minister David Cameron arrives an EU summit meeting on the so-called Brexit at the European Union headquarters in Brussels, on February 19, 2016
Stephane de Sakutin | AFP | Getty Images

Three years ago, Cameron, under pressure from euroskeptic members of his ruling Conservative party and Nigel Farage's U.K. Independence Party, pledged to renegotiate the U.K.'s terms of membership and then offer a public referendum on the country's membership.

The U.K. is set to hold the vote on Thursday, June 23. The ballot is set to ask: "Should the United Kingdom remain a member of the European Union or leave the European Union?" Voters will be asked to choose one of two options: "Remain a member of the European Union" or "Leave the European Union."

British and Irish citizens, as well as U.K. expats that have lived abroad for less than 15 years, are eligible to vote.

Commonwealth residents living in the UK — like those hailing from Canada, New Zealand, Australia and India — will also be able to cast their ballot. No other EU citizens — except those from Malta, Cyprus and Ireland — will be eligible.

All voters must be over the age of 18.

Nonetheless, some have bemoaned the timing of the result: It will take place during the UK's most popular music festival, Glastonbury, and the Euro 2016 soccer tournament.

Who’s on which side?

The referendum question has divided political parties and the business community.

David Cameron announced back in January that he would allow those government ministers that wanted to do so to campaign to leave the EU, despite concerns that it could split the Conservative Party.

Conservative cabinet members including Justice Minister Michael Gove, and the Minister for Employment Priti Patel have been joined by the likes of London Mayor Boris Johnson in calling for a Brexit, with some citing hopes of safeguarding UK democracy and others claiming that Britain is currently exposed to EU terror risks.

That's alongside business leaders like Reebok co-founder Joe Foster, Phones 4u co-founder John Caudwell, and hedge fund billionaire Crispin Odey, who have criticized profit-reducing regulations in Europe and say money sent to Brussels would be better spent at home.

Others like Chancellor George Osborne, Business Secretary Sajid Javid and Home Secretary Theresa May plan to campaign alongside Cameron to remain part of the EU. The leadership of the opposition Labour Party has also come out in favor of staying in Europe.

Heavy hitters like HSBC's CEO Stuart Gulliver, and WPP boss Martin Sorrell have joined the calls to remain, saying businesses are better positioned to benefit if they stay in the 28-nation bloc

Odds of a Brexit

London Mayor Boris Johnson
3 reasons why we should worry about a 'Brexit'

At this point it's anyone's guess as to how the referendum will play out, leaving some to wonder how prepared they should be in the case of a Brexit.

The most recent YouGov poll conducted at the start of February saw the "Leave" camp leading with 45 percent, and the "Remain" camp with only 36 percent, with 19 percent of those polled saying they either wouldn't vote or were undecided.

A similar poll from OpenEurope this month suggested that over 45 percent of voters aren't sure whether they'd personally be better off in or outside of the EU.

The Financial Times' referendum poll tracker, last updated February 20, showed the stay camp clocking 43 percent and the leave camp at 40 percent.

The fallout: How might Europe and the UK cope?

There are some serious questions about how Britain would deal with practical matters around trade and migration if it were to leave the EU.

The government would need to negotiate new bilateral trade agreements, including those with the EU, given the bloc accounted for over more than 44 percent of UK exports in 2014, according to the Office for National Statistics.

Decisions would also have to be made around migration, including about those EU citizens working in the UK, and UK citizens working abroad in Europe. It's not yet clear how large of an impact a new visa system would have on the continental and British economy.

There are also concerns about the integrity of the United Kingdom itself, with the Scottish National Party leadership already warning that a new independence referendum would most likely be demanded by Scotland in the case of a Brexit.

How will markets react?

Sterling fell to near six-year lows against the dollar on Monday, February 22, and saw its biggest one-day loss in 11 months after Cameron formally announced the June 23 referendum date over the weekend. Stock prices and the 10-year gilt yield, however, saw little change.

JPMorgan expects the UK to stay in Europe, but admits it's a "close call," according to an equity strategy note released February 22. They expect that if Britain does leave, knee-jerk reaction will send markets lower, but sterling weakness and action by the Bank of England would help cushion a fall in equities. Still, they warn that domestic stocks like retail and homebuilders may come under pressure if a Brexit takes hold.

However, investment banks like Berenberg have warned that leaving the EU would be "devastating" and "costly" for the Britain, according to a February 20 note by Senior UK Economist Kallum Pickering. He adds that the precedent of a Brexit would "send tremors across the Eurozone and its financial markets."

Pickering maintains that it's the key political tail risk to watch in Europe in 2016.