文章裏都有詳細解釋。抄錄兩段如下：

The money in the plan is treated as a gift from the current beneficiary to the new beneficiary if the new beneficiary is below the generation level of the current beneficiary. The current beneficiary, not the account owner, needs to deal with the gift tax and GST tax.

Name the youngest possible beneficiary when opening a 519 account. There is NO gift or GST tax when the the new beneficiary is at the same or above generation level of the current beneficiary.