Originally Posted by Henry17
If poker is your main source of income or a secondary source does not matter. The question of is it taxable income or a windfall is based on how you go about playing poker and has nothing to do with if you are employed or not.
This is a little imprecise.
The question is whether poker is giving rise to income "from a source." The determination of whether a particular activity gives rise to characterization as income "from a source" is not entirely independent of whether one has employment (though it is very close to being independent).
Here's why. Theoretically, poker is an arm's race. As a matter of epistemology, it is impossible to state at any moment whether one is ahead or behind in the poker arm's race. A significant track record of success is one indicia, as is relying on poker for one's livelihood, because of what it reveals about one's state of mind.
This is why, in my considered view, being employed full-time and playing casually for an hour a day can be treated conceptually differently from playing an hour a day with exactly the same cash flows--it gives rise to a substantively and qualitatively different subjective expectation of profit, which will be related on average with a higher objective expectation of profit. Of course, there are deluded ("unlucky") losers and deluded ("pro") winners, too, which render this only an "on average" conclusion.