What is the European Commission asking for from the UK?
Britain has been told it has to pay an extra £1.7bn (€2.1bn) towards the European Union budget.
This is being called a one-off bill which would add about a fifth to the UK's annual net contribution of £8.6bn.
Why the increase?
The extra money is being demanded because the UK economy is doing better relative to the sluggish eurozone.
Contributions are based on each member's VAT receipts and national income, and the adjustment takes into account the fluctuating size of economies.
Do any other countries have to pay more?
The Netherlands has been asked to stump up an extra €642m into the EU budget.
Do any countries have to pay less?
France is set to get a rebate of €1bn and Germany is due to receive a €779m rebate as they have been overpaying.
When does the UK have to pay the extra money?
Britain will have to make the top up payment by 1 December. Refusal to pay could result in legal action by the EU for "infraction".
However, the maximum fine for the UK would be €225m (£177m) a year - much less than the cost of the surcharge.
Why is the UK government angered by the extra demand?
David Cameron called the £1.7bn bill "completely unacceptable" at a meeting in Brussels and said he would not pay it by 1 December.
The surcharge was branded "outrageous" by Eurosceptic MPs in his Conservative Party.
And it will pile more pressure on the Prime Minister as he fights to defend the seat of Rochester and Strood from UKIP in a by-election on November 20.
What does UKIP think?
Leader Nigel Farage said: "David Cameron once claimed that he had reduced the EU budget - but the UK contribution went up - and now, quite incredibly, our contribution goes up a second time. It's just outrageous.
"The EU is like a thirsty vampire feasting on UK taxpayers' blood. We need to protect the innocent victims, who are us."
Maybe the UK should pay the extra money?
Lecturer Isabelle Hertner said she was in favour of the surcharge. She told Sky News: "It is fair because for many years Britain had a rebate that was negotiated by ex-PM Margaret Thatcher and paid less into the EU budget than it should have paid.
"Whereas Germany and France paid as much as it should have paid, so in a way this is a give-and-take relationship. Sometimes you pay in more, sometimes less.
"For me this is fair and it was a rule that was agreed by the British government and other EU governments in the past."
What does the European Commission say?
Patrizio Fiorilli, an EC spokesman, said the request for more funds "reflects an increase in wealth".
He said: "Just as in Britain you pay more to the Inland Revenue if your earnings go up."
The EC also said the EU budget was about €144bn in 2013 - which it claimed was very small compared to the sum of the 28 EU countries' national budgets (over €6,400bn).
It added that total government expenditure by the 28 EU countries is almost 50 times the EU budget.