Can I claim my mother as a dependant? She had cancer and passed away in August but I was her caregiver up until she passed can I add her as a dependant on my taxes?

Perhaps! You must meet all the qualifications to claim someone as a qualifying relative.  See the rules at the link below.

• Who can I claim as a dependent?

To claim a dependent, you must pay more than 50% of their expenses. This includes food, housing, clothes, medical and dental care, education, transportation, utilities, and other basic needs.

To determine this, compare how much you spend on this person's necessities with how much they (or somebody else) contribute.

• Divide per-household costs like utilities, groceries, and lodging by the number of household members to determine the per-person cost.
• If your mortgage is paid off, use the fair rental value of your home to figure out the lodging expense.

If you are paying more than 50% of another person's necessary living expenses, you financially support that person.

• What does financially support someone mean?

We are sorry for your loss.

If you met the tests while she was alive, then you can claim her even if she died during the year.  The important tests are, 

1. you paid more than half her support,

2. her taxable income was less than $5050.