CSC Response Codes

Card Security Code (CSC) is a security feature that protects against fraud. It ensures that credit card transactions can't be made without it being in the cardholder's possession.

Response Code	Message
M	The CSC matches the issuing bank’s records
N	The CSC does not match the issuing bank’s records
P	The CSC was not processed
S	The card should have a CSC, but merchant indicated it was not present
U	Card issuing bank does not participate
X	Unknown / No response