Customers may contact you to request a refund on your asset. However, as the purchase was made through the Asset Store, it should be the store that manages the refund - not individual publishers.
If possible, try to help your customer resolve their issue to avoid a refund. If a refund is required, then you must request it form the Asset Store on the customer’s behalf, using the following process:
Ask the user to provide you with the invoice they received when they purchased the asset.
Log in to your publisher administration page.
Verify the invoice using the Verify Invoice tab.
Once verified, email firstname.lastname@example.org from an email address attached to your publisher account. You must provide either the invoice as an attachment, or the invoice number.
Here is a template request:
Hi Asset Store Team, Please refund the following asset(s) Publisher Name: - Asset name(s) Regards