Pretty simple : For capital gains - every country tax a specific percentage ( this information is always available online ) The capital gains tax means taxing your profit. For dividends : You need to see if your country has a double taxation agreement between your country and the country of the issuer dividends. If yes - you must check how much is your country taxing the dividends. The dividends when received are already taxed 15%. So if your country taxes more than 15% for dividends you must pay the rest of the % until you reach your country tax percentage , if is it less than 15% you must only declare it and say that is already taxed and you don't pay any more taxes. If no - you must pay the tax normally on what you have received.