Spanish to English Bus/Financial Finance (general)

Dear Colleagues:

I am translating a bank statement from Spanish (Spain) to English (US). Throughout the statement the above term is included with a transaction and then followed by a number. In other transactions just a reference number is used. What sort of reference is this specifically? How would this best be translated into US English? Is it identifying a bank or merchant processing the transaction? The length of the numbers following Ref. Mandato ranges from 5 to 12 digits. Thank you all in advance for your help!

Best,

Douglas