Answer: it depends on how you look at it. I've put together the chart below (click for a larger version), which sets how much money we've given the the EU since 1973. There are three lines for each year: i) our gross contribution, ii) our total contribution (which is the gross contribution minus the money we get back from the rebate), and iii) the net contribution (gross contribution minus both the rebate and the money that the Treasury gets to pay for various EU projects across the UK). In terms of how much the EU costs the taxpayer, then, I'd say the second line is the best one to follow:
As for the future, there are no comparable figures yet (as the Treasury works in financial years, whereas the EU works in calendar years). But these are the projections made at the time of the Emergency Budget:
To put this into some sort of context, our net contribution to the EU is exceeded only by Germany.