Quote from Expatrader:
The 30% withholding applies to non-resident aliens from countries which do not have a tax treaty with the US.
For countries with treaties, the treaties themselves have different specifications for the tax liabilities on different types of income. You can locate tax treaties from the IRS website and download them.
Of most interest to traders, there are several countries whose nationals will get zero US-side liability for capital gains from investment/trading in stocks. In theory, the broker will send a statement to tax authorities of the foreign country in question, or the trader will 'honestly' claim the income. In reality, many places do not have anything set up to deal with this effectively, others have a cap gains rate quite a bit lower than the states.
The non-resident alien trader will have to apply for a US Taxpayer Identification Number in order to open the brokerage account a file the W-8 BEN to get exemption from the 30% withholding.
I have looked into this extensively as there is obviously potential for an edge here...
P.S. The benefit to the US of doing this is that those tax treaty countries extend likewise breaks to US people and companies working in their economies.
Expatrader, thx for valuable information. One Q: why using Taxpayer Identification Number you get exemption from 30% withholding ? Does Uncle Sam considers you then being under his jurisdiction ?