By whom? State or Feds?
Feds. Each time the audit was triggered because the IRS thought we were under reporting capital gains from the gains on the 529 accounts. Our accountant would send a letter explaining what it was and the IRS would agree. We never actually made an error on the returns nor did we have to pay more. It may have been how our account provider was reporting the information on their IRS submissions or it could have been a bug in the IRS software across-auditing the different reporting.