IRS says bonus paid to open a 529 is a 1099 event
The IRS views the bonus payment as a two-step transaction: (1) payment of cash to the customer (income subject to 1099 reporting), followed by (2) customer funding of his or her 529 account.
A similar type of bonus paid to a customer opening an IRA is not subject to 1099 reporting. The IRS distinguishes an IRA from a 529 plan and cites statutory authority for exempting the IRA bonus from 1099 reporting requirements.