You must be older than your sister and she must qualify as your dependent. If she has education expenses and you claim her as a dependent, then you will file Form 1098-T. Please view the qualifications for claiming a dependent below.

Rules for claiming a qualifying child:

• They're related to you.
• They aren't claimed as a dependent by someone else. (Do your parents qualify to claim her as a dependent?)
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They're under the age of 19 (or 24 for full-time students).
• No age limit for permanently and totally disabled children.
• They lived with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.

If your sister was 24 on 12/31/19, she may still qualify as your dependent if you meet the qualifications below:

Rules for claiming a qualifying relative:

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,200 in 2019.
• You provided more than half of their financial support.

Please follow the directions below to enter your sister as a dependent:

1. Log in and open your return
2. Click the My Info tab on the left side of the screen.
3. Click the add a dependent tab

In the personal info section of TurboTax (TT), you enter her information under dependents. Then you follow the interview. If she qualifies, TT will list her as your dependent.  She must qualify as your dependent in order for you to claim the tuition credit.

There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, student status, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit. So the interview is long and complicated.

In addition to the dependent rules, listed at the other post:

1. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child (this essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year)
2. If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child. (Your income is higher than the parents)