Click to Pay Customer Authentication {#ctp-authentication}
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When you enable customer authentication through Click to Pay, you give `Cybersource` permission to request that Visa and Mastercard provide an authenticated payload for each transaction. Authentication takes place within the authentication service of each card type. You must inspect the payload that is returned to you to determine if the transaction is authenticated.  
For information about enabling customer authentication through Click to Pay, see these topics:

* [Enable Click to Pay Customer Authentication Using the API](/docs/cybs/en-us/click-to-pay/developer/all/rest/click-to-pay/ctp-configuration-intro/ctp-authentication/boarding-click-to-pay-auth-enable-intro.md "")
* [Enable Click to Pay Customer Authentication Using the Business Center](/docs/cybs/en-us/click-to-pay/developer/all/rest/click-to-pay/ctp-configuration-intro/ctp-authentication/ctp-authentication-config-ebc.md "")
  {#ctp-authentication_ul_iyg_v1b_3jc}  
  When the customer completes a transaction using a Visa or Mastercard Click to Pay credentials, authentication is managed within Click to Pay. When the customer checks out using manual card entry and does not save their card to Click to Pay, the transaction is not processed through Click to Pay and you must complete authentication based on your existing authentication method.

> IMPORTANT
> American Express cards cannot be authenticated through Click to Pay customer authentication. You must use another authentication method for this card type.

Authentication Flow {#ctp-authentication_section_rkj_xcs_hjc}
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This image shows the Click to Pay authentication flow:  
![](/content/dam/documentation/cybs/en-us/topics/payments-processing/card-processing/click-to-pay/images/uc-ctp-auth-flow-vas-740x475.svg/jcr:content/renditions/original)