My daughter recently started college, and I'm looking at paying for it out of her 529 account.
A significant part of the cost is room and board. The IRS website about qualified educational expenses says that room and board are not a qualified expense:
but the SEC website says they are:
Who do I believe?
The IRS page you linked is under "Credits&Deductions" -- it applies to AOTC and LLC, and they indeed do not include room&board. 529 plans, formally Qualified Tuition Programs, are covered instead in pub 970 chapter 8 (note link is for 2020 version and may break in future; if so look in the ToC at top left under Qualified Tuition Programs for Qualified Higher Education Expenses) and item 3 says room&board are included for at-least-half-time students with a limit affected by whether they are in housing 'owned or operated' by the school -- that isn't quite the same as 'on-campus' in RonJohn's answer but it's pretty close.
Searching on the SEC website for "Qualified Higher Education Expenses" finds only pages about 529 plans referencing that glossary entry, which is probably why they define it that way (but it still isn't exact).
According to Merrill Lynch, on-campus room and board are qualified, while off-campus room and board are only qualified up to the cost of on-campus room and board.
Certain room and board expenses, which may include food purchased directly through the college or university (for the stipulations of off-campus living — see below)
For students living off campus, rent, utilities and food not purchased directly from the college or university may qualify, if those expenses do not exceed the allowance for room and board, as included in that institution's cost of attendance.
