Before everything "online" a bookstore would order books from a wholesaler. often via paper. Giving the wrong number would either result in order forms being se

Before everything "online" a bookstore would order books from a wholesaler. often via paper. Giving the wrong number would either result in order forms being sent back and force or wrong books being delivered which had to be returned (if possible at all). So having check digits seems like a cleve idea to reduce possible errors resulting in unneeded transactions. And International Bank Account Numbers (IBANs) have two check digits, but at the front, not at the back. And having check digits is important, because it might not be easy to get your money back, if transferred to some unintended account. The IBAN consists of up to 34 alphanumeric characters comprising a country code; two check digits; and a number that includes the domestic bank account number, branch identifier, and potential routing information. The check digits enable a check of the bank account number to confirm its integrity before submitting a transaction. https://en.wikipedia.org/wiki/International_Bank_Account_Number https://en.wikipedia.org/wiki/International_Bank_Account_Num...