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).
A person can still be a Qualifying relative dependent, if not a Qualifying Child, if he meets the 6 tests for claiming a dependent:
- Closely Related OR live with the taxpayer ALL year
- His/her gross taxable income for the year must be less than $4200 ($4150 in 2018)
- The taxpayer must have provided more than 1/2 his support
In either case:
- He must be a US citizen or resident of the US, Canada or Mexico
- He must not file a joint return with his spouse or be claiming a dependent of his own
- He must not be the qualifying child of another taxpayer
Nontaxable Social security doesn't count as income, for the income test, but social security money he/she spends on her self does count as support not provided by you, for the support test. Money she puts into savings & investment does not count as support she spent on herself. Note that a parent is closely related so there is no requirement that she live with you at any time, during the year. But if you provided a home it helps your support case, unless they own the home you live in. If no one person (or married couple) provides 50% of the support (for example your siblings are also sending support), then a "multiple support agreement” (IRS Form 2120) can be used, to allow you to claim the dependent. https://www.irs.gov/pub/irs-pdf/f2120.pdf
The IRS has a worksheet that can be used to help with the support calculation. See: http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf The support value of a home is the fair market rental value, divided by the number of occupants.
https://ttlc.intuit.com/questions/1894472-who-is-a-dependent (TT FAQ)
