When you cancel an event registration, a credit memo is created. A credit memo reduces the amount of a customer's previous invoice and can be applied to a different invoice as a payment or reduction.
Once the event registration is cancelled, the way that you handle the credit memo in your accounting practices becomes a business decision that should be based on your association's specific policies.
For example: Associations will typically use credit memos to apply the amount toward another open invoice. However, sometimes members will simply want a refund or aren't active enough to benefit in the short-term from a credit memo. You should be familiar with your association's refund policy in order to make the right call on what to do here.
If you determine that a refund is the best route for your member, QuickBooks Online suggests deleting the credit memo and issuing a refund receipt. Keep in mind that this will remove the credit memo in its entirety, so be sure to double check with your accountant if you are unsure.