The debits and credits of a refund will vary depending on how the refund is created.

If a refund is created by selecting to "Add a New Refund" from Records -> Refunds or by selecting "New Refund" from the Activity tab of a record, we will see the following debits and credits.

Refund:
Debit:  Accounts Receivable
Credit: Account defined on the refund billing item

Refund Check:
Debit:  Account defined on the refund billing item
Credit: Cash

If a refund is created by selecting to "Reverse this Payment as a Refund", we will see the following debits and credits. 

Refund:
Debit:  Accounts Receivable
Credit: Debit account of the transaction being reversed

Refund Check:
Debit:  Credit account of the Refund
Credit: Cash