I came across this article authored by a lawyer/CPA who claims that SSI is NOT counted as support provided by the qualifying child:
"Needs-based support, such as SSI, is not included as income nor counted as support provided by a qualifying child for this test. In addition, it is critically important to remember that qualifying child status also requires a residency requirement that is not required under the qualifying relative test; the qualifying child must live in the same household as the taxpayer for more than half the tax year.
By contrast, SSI is counted as support under the qualifying relative test. As a result, if a taxpayer's special needs child's sole source of income is SSI, the "dependent's status" will not be jeopardized under the qualifying child test, but requires further examination under the qualifying relative test as to whether the individual seeking dependent status has provided more than half of the qualifying relative's support."
The author is making a distinction between Qualifying Child (for dependent status) and Qualifying Relative, and stating that SSI is not considered support provided by the Qualifying Child.
Is he simply mistaken?