On Wednesday, there were media claims that the likely bill had risen sharply from €60bn to €100bn.
The figure was published by the FT which said it had based its calculations on new data from across Europe.
The paper said that if farm-related payments are added in, and compensation for UK shares of EU buildings and future likely payments to the UK are excluded, it is possible the EU could request a 12-figure financial settlement from Britain.
RELATED CONTENT
However, the chief UK negotiator, David Davis, said in a BBC radio interview on Wednesday there would be nothing to pay unless there is a trade deal.
The latest twist in the increasingly bitter debate about a Brexit financial settlement comes as Michel Barnier, the EU's chief negotiator, presented the European Commission's proposed negotiating directives that will form the basis of his mandate for the talks.
The negotiating blueprint is a legal document based on the newly approved political guidelines.
Barnier said there was no agreed figure, but that the UK and EU had entered into "mutual commitments" which must be honoured. "There is no Brexit bill. The final settlement is all about settling the accounts," he told reporters.
Speaking at a news conference in Brussels on Wednesday, Barnier again said that agreement on the UK's financial obligations, the rights of European citizens in Britain and the thorny topic of its border with Ireland must come first in the negotiations.
Barnier said the first phase of talks about the divorce proceedings could take up to 16 months.
He hoped to be in a position by October or November this year to reach a judgment on whether sufficient progress has been made in withdrawal negotiations to trigger the start of the next phase, involving talks on future trade arrangements.
Manfred Weber, Chair of Parliament's EPP group, tweeted, "Michel Barnier has the full support of the EPP group for the upcoming difficult Brexit negotiations. Unity of EU27 is key."
Syed Kamall, Chair of Parliament's ECR group, told this website, "What we've seen today is the first technical presentation of the EU27's position. It's important to remember this is the start of negotiations and not a final offer. There will be a bit of trying it on, but that's to be expected."
The British deputy added, "Progress will be made as the process evolves. Despite the headlines, there is political will from both sides for a mutually beneficial EU-UK deal. Once the negotiations begin, both sides will need to be patient and constructive."