Under PT law, probably considered a capital gain. This being the case, only Portugal has the right to tax this - see double tax treaty article 14-6. The rate would be 28% on capital gains, with the taxpayer having the choice of being taxed as per the tax tables (if more advantageous)

 

Thank you very much Tony!

 

Day trading gains are usually treated as short-term capital gains in the U.S., so they’re taxed like regular income. I kept a simple trading journal to track every trade, which made tax time way less painful and helped me see which moves were costing me more than they made. About foreign taxes, some of what you pay in Portugal can offset U.S. taxes, but it gets tricky.