What type of payment occurs while the customer is active in the checkout flow and can authenticate a payment?

In the context of the checkout flow, an on-session payment refers to transactions that occur while the customer is actively engaged in the payment process. During this phase, customers can authenticate their payment details—often through methods such as entering a credit card number, validating with 2-factor authentication, or confirming a payment via their banking app. This direct interaction improves security, as the customer is present to verify and authorize the payment in real time.

In contrast, off-session payments happen when a customer is not actively participating in the payment flow, typically when recurring transactions or subscriptions are involved, where the customer has authorized future payments in advance. Async payments involve delayed processing and don't require customer authentication at the moment of transaction. Refund payments are focused on reversing a transaction rather than completing a new payment, making them irrelevant to the question about active payment processes within the checkout flow.