Credit card companies can track purchases at US gun shops using new payment code in effort to flag suspicious sales

A new code for gun shop purchases will be introduced by Visa, Mastercard, and American Express in a win for gun control advocates.

According to Investopedia, a merchant category code is a four-digit number used to classify businesses. The merchant code would allow for more transparency when it comes to gun purchases.

The new merchant code was approved by the ISO, a group of standards bodies from more than 160 countries.

The news was reported by several outlets.

Gun-control activists say the new code will help track large or suspicious weapons purchases, while gun rights advocates argue that the new code is unfair to those buying firearms legally since it stigmatizes all gun shop purchases.

The new code will apply to all purchases at gun and ammunition stores, but not at other types of retailers.

The New York City comptroller said the move would help financial institutions flag suspicious activity and save lives.

In a statement Saturday, Visa acknowledged the change and said it would protect all legal commerce on the Visa network.

Mastercard announced Friday that it would protect customers' privacy while focusing on how it will be implemented by merchants and their banks.

American Express said in a statement that it will work to prevent illegal activity on its network.