Will it be £50bn? Will it be £36bn? In fact, no one has any idea how much it is going to cost to leave the European Union (EU) and we won’t find out until October.

The UK’s Brexit secretary David Davis has said that the EU and the UK will not have an agreed figure for the so-called Brexit divorce bill for at least two more months.

He told BBC Radio 4’s Today programme:

We’re going to talk it through very, very carefully, so at this stage we’re not going to commit, there won’t be a number by October or November, whenever it is.

The discussions over the exit bill are holding up talks between the two parties, as the EU wants an agreement on the final figure before they can carry on with talks about Britain’s relationship with the union.

Read more: Brexit leaders: who is the man in charge of Brexit, David Davis?

If a figure for the bill is agreed upon by October, that only leaves 18 months for the EU and the UK to thrash out the rest of the negotiations before the UK officially leaves the EU in March 2019, two years after UK prime minister Theresa May triggered Article 50.

However, Davis doesn’t seem sure that the UK will be out of the union by this date. He seems to think a Brexit transition could extend until the next parliamentary election, due by May 2022.

Davis said:

“It’s got to be done by the election. I would say the most likely is something like two years, maybe a bit shorter.”

The UK government is set to publish several position papers today to establish its ambitions for future relations with the bloc.

Today’s paper will focus on the customs arrangement between the two parties. It has proposed to set up an interim agreement to allow the free flow of trade in a temporary customs union.

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When asked if he thought Britain would have to pay to stay in the customs union, Davis told ITV television:

No, I don’t think (so). Well what happens in that interim period you have to leave to me to negotiate.