Negotiators in London and Brussels are now working hard to get a Brexit deal over the line | Andy Rain/EPA Britain’s Brexit bill revealed: £37.1B over 45 years Office for Budget Responsibility produces first concrete figures on UK’s future payments to the EU.

LONDON — Britain will pay £37.1 billion to the European Union over the next 45 years, finally clearing its “Brexit bill” in 2064, according to the U.K.’s independent budget forecasters.

In a document published alongside Chancellor Philip Hammond’s spring statement on the public finances Tuesday, the Office for Budget Responsibility said the U.K. would pay almost half of its outstanding commitments to Brussels by the end of 2020.

Between 2019, when Britain leaves the EU, and the end of 2020, the U.K. will pay £16.4 billion toward the EU’s seven-year budget.

Over the next seven years, between 2021 and the end of 2028, the U.K. will pay a further £18.2 billion toward projects that have been signed off but not yet paid for — the so-called reste à liquider.

On top of this, the U.K. is on the hook for a further £2.5 billion over the next 45 years to cover ongoing expenses such as the pensions of EU officials and MEPs.

The forecast is the first concrete breakdown of the Brexit bill to be published on either side of the Channel and goes some way to detailing the extent of the “dividend” that will be available to the Treasury as a result of leaving the EU.

According to the Office for Budget Responsibility, the U.K. will not make any net savings from leaving until at least 2020. Between 2021 and 2028 there will be a slow tapering-off of the payments to Brussels before they fall to relatively small amounts from then on.

The OBR said its forecasts were based on “broad-brush assumptions about the economy” but said there was now “sufficient clarity” about the final bill to produce a concrete figure.

“The December 2017 joint report by the UK and EU negotiators detailed the components of this settlement. The Treasury estimated at the time that it would amount to £35 billion to £39 billion," the report said.

“Using assumptions consistent with our central economic and fiscal forecasts, we estimate the settlement would cost £37.1 billion, with around 75 percent falling due within our five-year forecast period.”