There's a special pub the IRS has for runaways. But for the life of me I can't find it no matter what search terms I use. But here's what I can recall (to the best of my ability - it's been awhile.)
- Age matters. So what's their age on Dec 31 of the tax year?
- Student status matters. Was she enrolled in a qualified institution for *any* *one* *semester* during the tax year as a *full time* student?
- If the runaway did not live under your roof for at least half the tax year *AND* she lived with another family member for more than half the year, you can't claim her - the other family member may (or may not) be able to.
There's other things in there too. I"m still looking for the pub.
Under "ordinary" circumstances, the child is treated as living with you if they are away for a "temporary absence." Normally that means staying with grandma or going to summer camp but it also includes boarding school and college. I'm not sure why it would not apply here, so long as the child meets the age test (is 18 or less on 12/31/2020) and does not support themself more than 50% with an income, and is not staying with a "close" relative who could also claim them as a dependent (In this case, a "close" relative is the child's grandparents, aunts or uncles, or older sibling.)
Per the IRS pub 501 :
To meet this test, your child must have lived
with you for more than half the year. There are
exceptions for temporary absences, children
who were born or died during the year, kidnapped
children, and children of divorced or separated
Temporary absences. Your child is considered
to have lived with you during periods of
time when one of you, or both, are temporarily
absent due to special circumstances such as:
Military service, or
Detention in a juvenile facility.
Well, I have searched from the top of the high heavens to the deepest depths of hell, and I can not find that document, publication or tax topic that I know for a "fact" I saw on the IRS website a number of years back that specifically and explicitly covers the tax implications of what the IRS termed "runaway dependent children". At this point, I give up.