The EU membership fee is different to the Divorce settlement. The divorce settlement is for expenditure agreed in the previous budget period plus any future agreed expenditure (in future budget periods) and probable expenditure.Before I answer that question again. Tell me first do we pay the membership fee in advance to the EU or for the previous year?
I honestly do not know the answer., I'm hoping you do.
But the final actual figure of the membership fee is paid one year after the agreed budget, to allow for final calculations of the EU revenue and expenditure.
The budget for a year is determined in advance, but final calculations of payments required from each member state are not completed until after the budget year is over and information about revenue and expenditure is available, and correction mechanisms have been applied
https://en.wikipedia.org/wiki/Budget_of_the_European_Union
https://en.wikipedia.org/wiki/Budget_of_the_European_Union