In case a profit-seeking enterprise has no permanent establishment or business agent within the territory of the Republic of China, in the event of having income within the territory of the Republic of China as provided in Article 88, the tax withholder shall withhold the income tax payable in accordance with prescribed withholding rates; in case the taxpayer has income which does not fall within the withholding scope as provided in Article 88, the tax agent shall be responsible for calculating and compiling his or her annual income into related profit and loss categories and levying relevant tax rates on them respectively, in accordance with regulations, during the tax return filing period from May 1 to May 31 every year. (Article 73 of the Income Tax Act)