Can I add my mother as a dependent if I am financially providing for her?

How can I make my parent a dependent?
To seek dependent status for an adult family member, such as a father, mother, father-in-law, motherin-law, stepparent, or someone in loco parentis, DFAS will apply a financial test to determine
whether the family member receives over half of his/her income from the Servicemember. You must
submit the Servicemember’s or spouse’s birth certificate and proof of the relationship, DD Forms
137-3 and 1172 to show financial dependency, and proof of the family member’s identity to DFAS.
For someone loco parentis, this will include affidavits that that person stood in a parental capacity for
at least five years prior to the Servicemember (or spouse’s) 21st birthday.

If I have other questions, what should I do?
For additional information and points of contact, you may visit the DFAS website at
http://www.dfas.mil/militarymembers/payentitlements/secondarydependency.html
For appointments concerning dependents and other personal legal matters, call the Legal
Assistance Branch of the Office of the Staff Judge Advocate located at Building 358, Buffalo
Soldier Trail, Defense Language Institute, Presidion of Monterey [login to see] or DSN 768-
5085).

Google DFAS secondary dependent. It will provide you information. There is also a service specific link to tell you how to do this with the help of your chain of command. Your case will be evaluated on its own circumstances so it's not a clear cut yes or no. Gather the documents and do the research.

This question has been asked and answered on RP hundreds of times. Start in the search box.

A tangential comment. I’m not a tax lawyer or specialist, but it’s my understanding that if you are successful in claiming your mother as a dependent, that would also apply to your tax return. She could then no longer claim herself. Verify this with a tax specialist, and if true, make sure your mother understands and agrees to this course of action.