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The tax is generally withheld (NRA withholding) from the payment made to the foreign person.The following amounts are not subject to NRA withholding.
If your only U.S. business activity is trading in stocks, securities, or commodities (including hedging transactions) through a U.S. resident broker or other agent, you are NOT engaged in a trade or business in the United States. When a foreign person engages in a trade or business in the United States, all income from sources within the United States connected with the conduct of that trade or business is considered to be Effectively Connected Income (ECI). This applies whether or not there is any connection between the income, and the trade or business being carried on in the United States, during the tax year.
I am worried/suspiscious that I am being asked to pay the tax before conclusion/receipt of the monies from the sale of my shares and wonder why the tax cannot be witheld from the monies I will receive as you state is the general case. On what grounds can the dealer insist I pay in advance. (IMPORTANT NOTE:- The registered dealer, who is part of a Canadian company, PanAm Advisory based in Vancoever, approached me in the first instance saying he had a buyer willing to pay above the market price)