If you are a salaried employee receiving a salary from your employer, you must file a tax return if your profits from overseas forex trading exceed 200,000 yen. Tax returns are generally filed from February 16th to March 15th, and involve declaring your income from January 1st to December 31st of the previous year and calculating your taxes... Read more: A thorough explanation of tax calculation, tax filing, and tax saving strategies for salaried employees with overseas forex trading.