That 3-digit code on the back of the card...
Nov 28, 2004 | 2:51 am
#1
Original Poster
Join Date: Jan 2003
Posts: 30
That 3-digit code on the back of the card...
...what is it for? The CVC code is the 4-digit number on the face of the card, but there is a 3-digit sequence after the account number on the signature strip. Just a passing curiosity 
Nov 28, 2004 | 7:01 am
#5
Join Date: Apr 2004
Location: LAX
Programs: F9 Gold, peon and loving it everywhere else
Posts: 4,018
My Rewards Green card has a 3-digit code, but my Starwood (converted from Blue) does not. All Amex cards, of course, use a 4-digit CID number on the front of the card for "card not present" transactions.
Nov 28, 2004 | 10:33 am
#7
Join Date: Aug 2001
Location: Erie, CO USA
Programs: UA, M&M, AA, AS, Marriott, et al
Posts: 1,568
I don't know what it's used for, but I had a retailer want to enter it as the security code (as that is apparently how some Visa/MC's do it). The number on my card had faded too much to read. Since every other retailer had used the 4 digit number on the face, I suggested that this retailer use the 4 digit number, and it worked fine. In speaking with Amex Customer Service later, I mentioned the faded numbers and asked if I needed a new card; the person responded no, that those number are not used by the cardholder or retailers. I still don't know what they are, but apparently they really don't matter to us.
Nov 29, 2004 | 5:29 pm
#10
Join Date: Oct 2004
Location: SF, CA USA
Programs: UA 1K MM, RCC, PreChk , Hertz 5* Gold, HH Silver, SPG Gold thx to Amex Plat
Posts: 490
I don't see a 3-digit # on the back of my Plat charge card (expires 2005)...I believe Amex uses the 4-digit number on the front for verification.
The 3-digit number is used on Visa and MC cards for card verification purposes for mail/phone/e-comm transactions. The number is derived from an algorithm using your account number, plus other account data, to ensure that in a card-not-present transaction, the card is valid. If someone gets hold of your account number (e.g. stolen statement, receipt, etc), they cannot provide this number.
The 3-digit number is used on Visa and MC cards for card verification purposes for mail/phone/e-comm transactions. The number is derived from an algorithm using your account number, plus other account data, to ensure that in a card-not-present transaction, the card is valid. If someone gets hold of your account number (e.g. stolen statement, receipt, etc), they cannot provide this number.