Under certain circumstances, On Account sales (sales that are not paid immediately) can be returned. In order to do this, you have to search for the sale transaction (requires an active internet connection) and that transaction must be either be "Fully Open" (no payments have been made) or "Paid in Full".
If the transaction is "Fully Open" then you can only refund to payment method "On Account". If "Paid in Full", then refunds can be applied using the associated payment methods.
The Return Button will only be displayed, if a Return is allowed. If the Sale is "Partially Pad" or "Voided" a Return is not allowed