Notice 2018-58 provides rules that can be relied upon unless and until Treasury issues clarifying rules regarding the following:

K-12:  Distributions can be used to pay up to $10,000/yr of tuition per beneficiary at an elementary or secondary public, private or religious school.

Tuition Refunds:  A beneficiary receiving a refund of tuition or other qualified education expenses (e.g. dropping a class mid-semester) who re-contributes the money to any of their §529 plans within 60 days will be granted tax-free status on the refund.  Re-contributions would not count against the plan’s contribution limit.

ABLE Rollovers:  Money in a §529 can be rolled into an ABLE account for the same beneficiary.  Rollovers from 529s together with contributions to the designated beneficiary’s ABLE account cannot exceed the annual ABLE contribution limit ($15,000 for 2018).