You may claim a dependency exemption for a parent you support if the following are true:

1. The parent's gross income for 2017 is under $4,050 (social security benefits are treated as gross income only to the extent they are taxable).
2. You contributed over half of the parent's support for 2017.
3. You, or your spouse if filing jointly, cannot be claimed as a dependent by another taxpayer for the taxable year.
4. Your parent is a U.S. citizen or national, or a resident of the U.S., Canada, or Mexico for at least some part of the year.
5. If married, the parent cannot file a joint return, unless the return is only a claim for refund and neither spouse would owe tax on a separate return.

For more information refer to IRS Publication 501 Exemptions, Standard Deduction, and Filing Information. You may also wish to utilize the IRS Interactive Tax Assistant (ITA) topic Who can I claim as a dependent?