Age

• You can claim your child as a dependent until she reaches age 19. However, if your child attends school full-time, you can claim her as a dependent until the end of the year in which she turns 24. Even if you support your 25-year old child through graduate school, you can no longer claim her as a dependent unless she is permanently disabled. To be a dependent child, the relative you claim must be younger than you are, or younger than you or your spouse if you are married filing jointly. Therefore, you can claim your spouse's older sister as a dependent, as long as she is under 24 years of age and younger than you are.
  
  

Full-Time Student

• To qualify as a full-time student, your child must be enrolled in a high school, vocational school, college, university, technical or training school for at least five months out of the year. The months don't have to be consecutive. Schools that offer courses solely through the Internet or through correspondence courses don't qualify for full-time student status.
  
  

Residency

• Most dependents you claim on your taxes must live with you for more than half the year. However, the IRS makes an exception for a student who lives away at school. The IRS considers school as a temporary absence for tax purposes.
  
  

Support

• You can claim a qualifying child as a dependent if you provide more than half of the child's support. Scholarships don't figure into this computation. Therefore, even if you don't pay for your child's schooling or his room and board because he has a scholarship, you may still claim him as a dependent if you provide other support, such as spending money, a car, clothing or a place to live during school breaks. However, if your child works while he goes to school, pays for his own car and clothing, and only stays with you during breaks, you may have to prove that the support you provide is equal to more than the wages he claims on his personal tax return. If your child earns $6000 from a part-time job at school and your support equals only $4000, you can't claim him as a dependent. In addition, you can't claim your child as a dependent if he marries and files a joint return.