Non-resident alien individuals are taxed on income, after allowable expenses and deductions, that is effectively connected with a trade or business in the United States. The income is taxed at graduated rates which are the same rates that apply to United States citizens and residents.
Non-resident alien individuals are also taxed on United States source non-business income. Non-business income is considered to interest, dividends, royalties, commissions etc. The non-business income is taxed at a flat 30% or the lower treaty rate and no deductions are allowed against such income.