Several higher education institutions are issuing partial refunds for tuition and other expenses because of closures due to COVID-19. If you’ve taken a distribution from a 529 account to pay for tuition or other qualified expenses for an Eligible Educational Institution (e.g. higher education institutions with FAFSA codes), and have since received a refund, you can put that money back into the 529 and avoid federal taxation and the 10% withdrawal penalty. You have until July 15, 2020 to recontribute this money to the 529. State taxation and penalties vary in this case, so be sure to look into how your state is handling this.
See the Maryland 529 website for additional information and resources: https://maryland529.com/MarketVolatilityResources