I knew that, eventually, I would have to start paying quarterly estimated income taxes because of income from my shareware. I just wasn't aware of what the threshold would be for that, considering the addition of that and also deductions for homeowner-related and other stuff, and the fact that when I started it I didn't expect it to take off as well as it did. I just found out, rather painfully, that I've not only met but exceeded that mark, when I did my tax return and found out that I owe almost $3800 (state and fed combined). I did manage to escape a penalty on that, though, due to the way that those are figured.
Luckily, I will be able to manage that, especially with the money coming in from the sale of my old car. I won't be bitten in the ass like that again, though... this year begins my estimated tax payments :-)
Ya know, it'll certainly be nice if they manage to abolish the IRS, at least as we currently know it.