Regulations Governing the Withholding of Tax on Income from Salaries and Wages Article 5

As to salaries paid monthly whose recipient submits Tax Exemption Declarations in accordance with Paragraph 1, Article 3, tax withholders shall withhold tax at the time of payment each month based on the tax payable listed on the Withholding Tax Table for Income from Salaries and Wages by referring to whether the recipient of salaries and wages has a spouse and the number of his/her dependents.For the recipient of salaries who comes into the situations prescribed in Paragraph 2, Article 3, in which he/she gets married or whose number of dependents increases, tax withholders shall withhold tax based on the relevant change of information starting from the month of occurrence; for one who gets divorced, suffers from the death of his/her spouse, or whose number of dependents decreases, tax withholders shall withhold tax based on the change of information starting from January 1 of the following year.
中文原文 薪資所得扣繳辦法第5條
按月給付之薪資,受領人已依第三條第一項規定填報免稅額申報表者,扣繳義務人於每月給付薪資時,應按各薪資受領人有無配偶及受扶養親屬人數,適用薪資所得扣繳稅額表之規定,就其有無配偶、受扶養親屬人數及全月薪資數額,分別按表列應扣稅額,扣取稅款。
前項薪資受領人有第三條第二項規定異動情形,其為結婚或增加受扶養親屬人數者,扣繳義務人應自其異動發生之月份起,依異動情形辦理扣繳;其為離婚、配偶死亡或減少受扶養親屬人數者,應自次年一月一日起,依其異動情形辦理扣繳。

English translation for reference only; the Chinese text prevails. Not legal advice.