There are many different reasons why a payment may not succeed. However, many payments fail for good reason and do so to minimise the possibility of a fraudulent payment. The two main categories of failed payments are Declines and Blocked payments.
There are three possible reasons why a credit card payment might fail:
Typically, with a declined payment, a decline code will be sent by the issuer bank. To view a list of decline codes and what each code means, take a look at the Decline codes page.
You can read more about card declines and how to address them on the Declines page.
Certain failed payments might be preventative measures that work in your favour to minimise the possibility of a fraudulent payment, that could otherwise result in a dispute.
Examples of this are cards that are picked up by Stripe Radar as fraudulent or that match custom Radar rules created by you to filter out transactions that you do not want to accept. Payments that are picked up by Radar rules will be blocked as part of fraud prevention.
You can read more about built-in Radar rules on the Radar Rules page.