Geektastic: Tax should be due on money you have earned. Not on money you might earn.
Yep. A few years ago I made a large one-off sale and had to pay a decent chunk of tax. 'The system' decided that I'd apparently be doing the same every year, and I had to pay a decent chunk of provisional tax (which of course doesn't earn me interest when it's sitting in IRD's account instead of mine) only to get it all paid back again a year later.