For what it's worth:
At least two users have reported receiving a CP2000 letter, from the IRS, on 529 distributions. They replied that their child was in college and the distributions were for qualified expenses, which they listed, but they did not provide receipts.. They later received a notices saying they were in the clear.
I too once received a CP2000. I sent em a copy of the school's billing statement. That satisfied em.
