Where?
Google something like “529 room and board living at home” and you’ll get
multiple references.
The
bottom line is:
You
may exclude your actual cost or the school's aid allowance, which ever is
less. You may need to check with your child’s school to learn the room and
board allowance for students living at home with parents. It’s likely to be
less than off-campus students living independently.
You’ll also find similar language in IRS pub
970, chapter 8. https://www.irs.gov/pub/irs-pdf/p970.pdf
