The EU can hardly present an itemized bill when they have no idea what kind of Brexit the UK wants.
It's the EU that is refusing to negotiate the kind of Brexit the UK
will get until the, so-called, 'divorce bill' is agreed.
We know exactly what kind of Brexit the UK
wants, and it's a continued lie from the remainers to keep saying that the UK has no idea.
What Britain
wants is for all trading conditions to remain exactly as at present but for Britain to be able to control its own immigration and laws.
Now realistically, in any negotiation, neither side gets exactly what it wants, but to repeatedly say that it's not clear what the UK wants is a lie.
As long as the EU persists with its current stance of demanding the signing of a blank cheque there is no chance of progress. The EU must discuss possible future arrangements and assign a cost to the UK for each of the possible options. The UK can then haggle over the final agreed cost and decide which, if any, of the proposed deals is worth taking.
It's no surprise that the EU are delaying the negotiations. This has been the pattern of every EU negotiation ever. The EU delights in delay, brinkmanship, and eleventh-hour deals. Actually they never finish by the eleventh hour and the final discussions always go on all night and are often extended into subsequent days after any agreed deadline.