# Duplicate Subscription Check Plugin The **Duplicate Subscription Check** plugin helps prevent users from purchasing a subscription if they already have an active subscription for the same product. This ensures that customers do not accidentally purchase duplicate subscriptions. ## How It Works * The plugin integrates into the **order processing flow** and depends on the **Salesforce V3 plugin** running first. * This allows it to work across **authenticated, unauthenticated, and** [**anonymously authenticated**](https://docs.limio.com/product/authentication/authentication-provider-per-page/configuring-anonymous-authentication-for-your-checkout-flow) checkout flows. ## Checking for Existing Subscriptions * In **unauthenticated or** [**anonymously authenticated**](https://docs.limio.com/product/authentication/authentication-provider-per-page/configuring-anonymous-authentication-for-your-checkout-flow) checkouts, the Salesforce V3 plugin first determines if the user already has an account. * If a matching account is found, based on the set duplication rules, it passes the **crmID** forward. * The Salesforce V3 plugin then checks if the account associated with this `crmID` has an existing subscription in Limio. * For Express Apple Pay, the next expected step would be for the [**Transfer Ownership**](https://docs.limio.com/integrations/populating-salesforce-data/limio-updates-salesforce) to then run. ## Blocking Duplicate Subscriptions * If an **active, matching subscription** is found the Duplicate Subscription Check plugin will **throw an error**. * The user will not be able to complete the order and will see an error message in the checkout or express checkout offer page. This functionality is supported for **Express Apple Pay** and the **standard checkout flow**. To enable this plugin email .