Answer:

1. Article 15 of the Income Tax Act stipulates that the income of a married couple must be filed jointly except when the married couple could hardly maintain their common living, and have not lived together for more than 6 months conforming to Paragraph 2, Article 1010 of the Civil Code, or do not continue their cohabitation for more than 6 months, or one of the married couple have obtained an ordinary protection order conforming to Article 1089-1 of the Civil Code. However, the tax due on the spouse's salary or categorized income may be chosen to be calculated separately (please refer to Question No. 10). In the case of husband and wife living in different areas, either the husband or the wife can be the taxpayer and file the income tax return jointly at his/her district National Taxation Bureau.
2. For any non-resident having R.O.C.-source income and whose spouse is a resident of the R.O.C., the non-resident may choose to file his/her income tax return jointly with the spouse or file his/her own income at the tax rate of non-residents. If the non-resident chooses to file separately, his/her income should not be included in the consolidated income of the resident spouse. Also, the tax withheld and the tax due paid by a non-resident cannot be credited by the resident spouse, nor can an exemption and deduction be claimed when calculating the resident spouse's tax due.
3. In the case that a couple gets married or divorced during the interim of the year, they may choose to file income tax returns separately only for that related fiscal year. Presentation of a certificate of marriage or divorce is required at the time of filing. Further, double claiming is not permitted; the couple should determine which party may claim the related dependent's exemption(s); otherwise, such exemptions should be claimed by the person who actually provides financial support.

Besides the three different situations mentioned above, a resident of the R.O.C. should file the gross consolidated incomes for him/herself, his/her spouse, and his/her dependents jointly.