Old Feb 14, 15, 3:51 pm
  #15  
mia
A FlyerTalk Posting Legend, Moderator: American Express, Citi, Diners Club, Signatures
 
Join Date: Jun 2003
Location: Miami & London
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Posts: 41,163
Citi issues cards on three networks Here is Citi's explanation of how each network calculates exchange rates. Note that no network makes the conversion based on the transaction date. It is always tied to the posting date. See if there is a basis to choose one over another based on the processes rather than anecdotal reports or vague generalizations.

Information on Foreign Currency Conversion
Our network providers are MasterCard, Visa, and American Express. They convert transactions in foreign currencies into U.S. dollars. The type of card you have determines who does the conversion. Each network provider follows its own procedures. Each network provider’s current procedures are described below. The procedures may change from time to time without notice.

MasterCard uses a conversion rate in effect one day
before its transaction processing date
. It uses a
government-mandated rate if required to do so. If not,
it uses a wholesale market rate.

Visa uses a conversion rate in effect on its applicable
central processing date
. It uses a government-mandated
rate if required to do so. If not, it selects from the range
of rates available in wholesale currency markets. The
selected rate may vary from the rate Visa receives.

American Express uses any conversion rate required
by applicable law. If there is none, it uses the highest
interbank rate
it selects on the business day before the
day it processes the transaction.
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