taler-docs

commit 6ab70cee59b805bc897cd6de1962e17445294a44
parent be3acc22d3aef9535e4dea8c85d2f5defd73c338
Author: Christian Grothoff <christian@grothoff.org>
Date:   Tue,  7 Dec 2021 13:30:33 +0100

fees fees fees

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design-documents/026-refund-fees.rst
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+Refunds and Fees
+################
+
+Summary
+=======
+
+This document discusses what should happen with deposit fees when a
+deposit is refunded.
+
+
+Motivation
+==========
+
+When a user receives a refund, we have to decide what happens to the deposit
+fee that was originally paid on the associated deposit.  Originally, we said
+that the deposit fee is waived when any refund happens.  However, if the
+refund fee is zero and the deposit fee is non-zero, this results in a
+problematic scenario where merchants issue miniscule refunds that primarily
+enable customers to effectively obtain the deposit fee.
+
+
+Requirements
+============
+
+  * If the refund and refresh fees are zero, it should be possible for
+    consumers to get 100% of their digital cash back on refunds.
+  * This should not result in a problematic situation where merchants
+    conspire with consumers and issue miniscule refunds to allow consumers
+    to work around deposit fees.
+
+Proposed Solution
+=================
+
+  * Only waive the deposit fee for full refunds where for the
+    specific coin (!) the refunded amount is the total value of the
+    refunded deposit.
+
+Alternatives
+============
+
+  * Only waive the deposit fee for full refunds where for the
+    specific coin the refunded amount is the total value of the
+    denomination of the coin. This may slightly simplify the
+    logic, but has the problem that it does not enable 100%
+    refunds if the original payment already required a refresh
+    because the coin's value exceeded the paid amount.
+  * Waive the deposit fee on any (including partial) refund.
+    This creates a bad incentive structure if combined refresh
+    and refund fees are below deposit fees.
+
+Drawbacks
+=========
+
+  * We need to update and test an already complex fee calculation
+    logic.
+
+
+Discussion / Q&A
+================
+
+(This should be filled in with results from discussions on mailing lists / personal communication.)