The Duplicate Check option prevents customers from placing multiple orders for the same product using the same credit card. This is particularly useful for trial subscriptions and one-time offers where you want to limit customers to one purchase per payment method.
How to Enable Duplicate Checking
Go to Settings in the main navigation.
Click the Account settings button in the organization preview section.
Click the Personal Information tab.
Toggle the Duplicate Check switch to enable.
Click Save to apply your settings.