You can claim your ex-spouse as an exemption only if he meets all the following rules:
- Gross Income: He earns less than $4,050 in 2016.
- Total Support: You provide more than half of the total support for the year. - Support Test
- Member of Household or Relationship: He must live with you all year.
- He is not claimed by another taxpayer.
Your ex-spouse also needs to meet one of the followings:
1. a U.S citizen / greencard holder, or
2. a national of U.S possession or
3. a resident alien ( by meeting the Substantial Presence Test ) or
4. a resident of Canada or Mexico .