Can I claim my 18 year old who lived with me half of the year?

Yes, you may be able to claim the dependent exemption for your daughter if she qualifies.

If your daughter is your dependent but she is required to file, she must indicate (on her tax return) that she is being claimed by someone else. In that case, she will not receive an exemption for herself (exemptions cannot be split between two returns).

To claim dependency for her, she must:

1. Be the taxpayer’s child, stepchild, eligible foster child, brother, sister, stepbrother, stepsister, niece, nephew, or descendant of any of them.
2. Be younger than taxpayer and either under age 19 or a full-time student under age 24; or any age if totally and permanently disabled.
3. Live with the taxpayer more than half the year (being away for school qualifies as "lived with")
4. Not provide more than half of his/her own support. (Publication 501, page 16)
5. Not file a joint return (unless filed only to claim a refund).
6. Not be a qualifying child of another taxpayer with higher priority under the tie-breaker rules.

For 2016, a dependent must file a return if:

• his/her unearned income was more than $1,050
• his/her earned income was more than $6,300
• his/her gross income was more than the larger of: $1,050 or earned income of $5,950 plus $350.