The UK government says it does not recognise the EU estimate and believes the bill stands at between $48-53 billion – a discrepancy that could become the latest bone of contention between the two sides.
The European Commission has warned that its calculation of the cost of the Brexit divorce bill is final, after London and Brussels gave different estimates of what is owed.
Accounts published last month by the European Union give a figure of 47.5 billion euros [$56.5 billion] that Brussels says it is owed by the UK government, to be paid over several years.
A UK government spokesperson, however, said its estimate of the bill still stands at between 41 and 45 billion euros [$53 billion].
The discrepancy could become the latest bone of contention between the two sides already at loggerheads over several parts of the UK-EU withdrawal agreement.
Money owed by EU to UK
But European Commission spokesman Balazs Ujvari said the first instalment of Britain's 6.8 billion euro bill [$8 billion] for 2021 had been paid on time and in full.
"The report is final," Ujvari said, referring to the 200-page EU annual accounts published on June 30.
"And the calculations were made in line with the withdrawal agreement.
He said the bill amounts to "47.5 billion euros [$56.5 billion], which the United Kingdom is going to have to pay into the European Union budget over the course of the next years."
Separately, a British spokesperson said: "The UK Government's estimate of the value of the net financial settlement remains in the central range of 35 to 39 billion pounds [$54 billion].
The British official said the government does not recognise the higher Brussels figure and dubbed it "an estimate produced by the EU for its own internal accounting purposes.
"It doesn't, for instance, reflect money owed back to the UK, which reduces the amount we pay," the spokesperson told reporters.
Britain left the European Union at the start of the year after long and tortuous negotiations for a follow on trade and cooperation agreement with the 27-nation bloc.
But it agreed to ongoing payments, largely to reflect its obligation to support pension funds and sickness insurance for EU officials.
The EU spokesman said Britain would receive two bills this year totalling 6.8 billion euros [$8 billion] and that a first installment covering part of this sum had been paid in June.
"Everything that had to be done was done. Therefore, we have no indication whatsoever that the overall figure would be contested," Ujvari said
British leader Prime Minister Boris Johnson's government is to report full details of its estimate to the UK parliament "shortly".