Supplier Reference Number contained in the American Express Level 2 addendum.
This property contains a reference number that is used by American Express to obtain supporting information on a charge from a Merchant. Supporting documentation should be readily available in case of inquiry. The number can be any combination of characters and numerals defined by the Merchant or Authorized Processor. However, it must be an index to the Merchant's record, so that charge information can be readily retrieved and promptly submitted within 10 calendar days (or within the period stipulated in the contractual agreement). This number appears on the card member descriptive billing and Merchant inquiry reports.
The maximum length for this property is 9 characters.