A lot depends on your age. There are two types of dependency tests, one for a "child" and one for relative. I will include both. Support might be the main issue here. It is worded differently for both tests, but you will still have to accurately account for every dollar spent for support from othe sides.
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
In general, to be a taxpayer’s
qualifying child, a person must satisfy four tests:
Relationship — the taxpayer’s child or stepchild (whether by
blood or adoption), foster child, sibling or step-sibling, or a descendant of
one of these.
Residence — has the same principal residence as the taxpayer
for more than half the tax year. Exceptions apply, in certain cases, for
children of divorced or separated parents, kidnapped children, temporary
absences, and for children who were born or died during the year.
Age — must be under the age of 19 at the end of the tax
year, or under the age of 24 if a full-time student for at least five months of
the year, or be permanently and totally disabled at any time during the year.
Support — did not provide more than one-half of his/her own
support for the year
Qualifying
Relative.
- Do they live
with you? Your relative must live at your residence all year or be on the
list of “relatives who do not live with you” in Publication 501. About 30 types of relatives are on this
list.
- Do they make less
than $4,050? Your relative cannot have a gross income of more
than $4,050 and be claimed by you as a dependent.
- Do you financially support
them? You must provide more than half of your relative’s total
support each year.
- Are they a
citizen or resident? The person must be a U.S. citizen, a U.S.
national, a U.S. resident, or a resident of Canada or Mexico. Many people
wonder if they can claim a foreign-exchange student who temporarily lives
with them. The answer is maybe, but only if they meet this requirement.
- Are you the
only person claiming them as a dependent? You can’t claim someone who
takes a personal exemption for himself or claims another dependent on his
own tax form.
- Are they
filing a joint return? You cannot claim someone who is married and
files a joint tax return. Say you support your married teen-aged son: If
he files a joint return with his spouse, you can’t claim him as a
dependent
