Do you have to declare stuff? Do you only have to declare, after a certain amount? Does it depend on the broker? How does this stuff work in general? That's my question. As always, thank you for your time in advance guys!
It's basically like any other form of business / investment / self employment income. You get a statement at the end of the year, a copy of which is of course sent to the good ole IRS in the US. You can write off a certain amount of realized losses and carry forward to future years amounts beyond that limit - as long as you don't reinvest in the security that you're using to write off a loss on within 30 days of realizing that loss. http://www.irs.gov/uac/IRS-Reminds-Taxpayers-They-Can-Use-Stock-Losses-to-Reduce-Taxes If investing / trading is your primary source of income, you can likely write off expenses - office equipment, perhaps some professional trading / investing software / hardware costs, educational materials, etc. Taxes can be pretty complicated. I'd recommend letting a tax expert do your taxes if possible.
Obviously each country has different laws about taxation but I would be highly surprised if you wouldn't be required to report each and every $ you earn. As JR said, with any online broker you should find a yearly statement (often there is a special tax statement) which has all the necessary info. This is also the info the IRS (or your national equivalent) will be getting from the broker if they request it. Also in quite a few countries dividends and realized profits are taxed in a different manner, so be sure to understand the difference and see how it affects your investments.
Of course if you did the smart thing and set up an account as a Roth or traditional IRA (depending upon your income level), taxes will be deferred and eventually not a factor with the Roth.
Tax questions are too person-specific to give an answer really, and how you structure your income streams with respect to your own tax status is crucial. But with stock market trading, you should, by way of a good tax adviser or accountant, get away with paying only a small fraction of it in tax. At least that's my experience here in the UK.
