EU referendum: What happens if it's a dead heat?

For weeks, reporters have been saying the EU referendum race is too close to call. Polls have swung back and forth, but the rolling average has put the two sides neck and neck.

And a recent analysis of polling data and turnout figures by the Press Association found that the result could be very close indeed. "The EU referendum could end as a dead heat between Remain and Leave," says ITV News, "if the difference in turnout between young and old voters mirrors the 2015 general election."

So what happens if the outcome is a true dead heat, with the national count evenly split between the two sides?

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The answer, it seems, is that nobody knows.

"We asked a range of people who we thought might know," says the Daily Telegraph. "The electoral commission, the Commons, the Home Office, the Cabinet Office, and even the Foreign Office - but none were able to give us much of a steer."

A very close result is likely to result in legal action, says The Conversation, and it's likely to focus on overseas postal votes. At the 2015 general election, "some never arrived, or arrived late, meaning that many overseas voters' ballot papers were either lost or not counted".

In general elections, a dead heat at the national level is solved by coalition negotiations, and at a constituency level by the toss of a coin, with the winner becoming an MP. But the former method doesn't apply in an in-out referendum, and the latter has not been written in to the legislation for today's vote.

In the extremely unlike result of a mathematical tie, it seems likely that Parliament would decide the matter – not least because the referendum is not, in fact, legally binding.

"It's an advisory referendum," a government spokesman told the Telegraph, "so Parliament is likely to advise but it's a matter for the Government."

If the outcome is clear, Parliament is unlikely to overrule the public will, but in the event of a dead heat, it might express the preference of the overwhelming majority of MPs – to remain.