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Fraud prevention is a major concern for many people. To prevent fraudulent charges, most merchants require customers to provide their debit or credit card number, its expiration date and a numeric code — known as a card security code — located on their card. The CSC provides an important layer of security for cardholders.

A card security code is a three- or four-digit number on the back of credit and debit cards that ensures the authenticity of transactions when a physical card is not presented at the point of sale. American Express® cards have the security code on the front of the card.

Typically, these transactions occur over the phone or on the internet when people order products and services remotely. CSCs were created to help merchants verify that the purchaser is authorized to use the credit or debit card when the merchant cannot see the card or the purchaser.

Essentially, a CSC is a feature that provides an additional layer of safety and security for shoppers, protects merchants from fraud and prevents chargebacks.

Credit card providers require retailers to honor losses on disputed and fraudulent transactions. A chargeback charge is returned to a bank payment card after a consumer successfully disputes a transaction made on their credit or debit card account statement.

A cardholder must be in possession of their physical credit or debit card to find, check and enter the card’s CSC. They should immediately contact the card issuer if the card is misplaced, lost or stolen or if the CSC is no longer legible on the card. Typically, the bank will issue a new card right away.

Since card security codes can only be found on physical credit and debit cards, unfortunately, bank cardholders will not find their CSCs on their bank statements or by looking at their accounts online. Since the CSC number only exists on the cards themselves, it may be wise for cardholders to memorize their card numbers and CSC numbers and keep the information private for maximum security.

Using CSC numbers protects consumers from credit card fraud. The payment card industry has standards that enforce CSC safety by prohibiting merchants from storing sensitive CSC data.

On the other hand, these standards do not forbid merchants from storing credit and debit card numbers, leaving them susceptible to card fraud. However, having access to a debit or credit card number without the CSC makes it more difficult for imposters to commit card fraud.

More people are shopping online and using their credit and debit cards to pay for purchases. Online retailers require their customers to manually enter their card numbers and CSC numbers when making purchases.

Merchants also request additional customer information such as their billing address and debit or credit card expiration date. All of this information together provides extra security and protection for customers against fraudulent purchases.

Sometimes credit or debit card chargebacks can occur during purchases even when customers and merchants enter the correct CSC. Here are some example situations with explanations of how card fraud can happen.

The three- or four-digit code on credit and debit cards can be either a card security code or a card verification value. A three-digit CVV is located on the back of Mastercard®, VISA® and Discover® cards. CVV2 numbers are CVV numbers that are generated by a second-generation process that makes the numbers more difficult for would-be frauds to guess.

CSC numbers are also referred to as:

For American Express, the four-digit CID code is usually located on the front of the card to the right of or slightly above the card number. The CID is printed on the card but is not raised or embossed. 

On Visa, Discover and Mastercard cards, the CSC is typically printed in the signature field toward the right of the card and after the credit or debit card number. 

When customers use their credit or debit cards for in-person purchases, merchants have no need to verify the card using its CSC. Security is ensured and data is authenticated either by swiping the card, tapping it on a contactless payment machine or inserting it into a chip reader.

Online and over-the-phone purchases where a physical bank card isn’t used to pay for items are called card-not-present, or CNP, transactions.

EMV chips are small, square computer chips found on most debit, credit and prepaid cards that help safeguard them from fraudulent use. Each chip has a unique code for each credit or debit transaction. Just like magnetic strips, EMV chips transmit payment data.

When a credit or debit card is inserted into a payment terminal, the terminal reads the chip’s data and authenticates and authorizes the purchase.

Cardholders should exercise caution when sharing CSC numbers with others. Imposters are savvy at pretending to be trusted merchants, especially over the phone. Credit and debit cardholders should beware of persons contacting them stating that they are a merchant or a bank representative from a credit card network.

Phishing scams are on the rise, and consumers are increasingly becoming victims of persons pretending to represent legitimate businesses, creating fake e-commerce sites that fool people into entering their credit and debit card information, including their CSCs.

In some cases, however, it’s acceptable or necessary for people to give out their credit or debit card’s CSC number. For instance, it’s safe to share a card’s CSC with merchants when making purchases online via a secure website or webpage. Also, when making a credit or debit card purchase directly with a merchant over the phone, it’s generally safe to share a CSC number.

Some scammers already have access to people’s credit and debit card numbers, and all that’s missing to complete a fraudulent act is an accurate CSC number. Cardholders should always attempt to verify the identity of the person they’re speaking with when ordering goods and services over the phone and also when making purchases online. 

Cardholders should avoid giving out their credit and debit card numbers as well as their CSC numbers to anyone not trusted or authorized.

They should make sure that any computers used are malware-free and check that the lock icon is visible in a web browser to confirm a secure and encrypted connection before making an online purchase and providing any card information.

Consumers should be sure to contact their card issuer immediately if they suspect any fraud, compromise or impropriety during a credit or debit card transaction.

If a customer’s credit or debit card is lost or stolen, they have limited liability for any resulting fraudulent transactions if they report the lost or stolen activity to the Federal Trade Commission in time.

This limited liability is only offered to bank card customers, and the majority of all of the fraud loss falls on the merchant or the bank itself. Both merchants and consumers can benefit from using CSC numbers to prevent card fraud.

Depending on the bank or credit card network, there may be some additional recourse for cardholders who find themselves victims of credit card scams. If caught in time, banks can offer customers guaranteed zero liability if they experience credit or debit card fraud. Again, merchants unfortunately don’t usually receive the same protection. 

Merchants should always prioritize the security of their customers’ debit and credit card security codes. Here are some ways that merchants can add extra layers of protection to CSCs:

Three- and four-digit CSC numbers let merchants know that customers have the debit or credit card they are trying to use to make a purchase in their possession. These codes protect both merchants and consumers from potential bank card fraud.

When merchants can’t verify a customer’s identity online or over the phone with a photo ID or by matching the signature on the back of a card with the signature on a receipt, CSCs can prevent credit card fraud.

It’s important to remember that a CSC or CVV number is not a credit or debit card’s personal identification number. PINs are used when making in-person POS transactions and at automated teller machines.

The bottom line? Providing a credit or debit card CSC number helps prevent fraud, especially when a culprit doesn’t have access to the code because they stole a credit or debit card number and don’t have the physical card in their possession.

CSCs and CVVs help keep customers’ card information safe when shopping online and when making transactions over the phone. It’s worth guarding them at all times.

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