What is required for a transaction to be completed in the card payment process?

For a transaction to be completed in the card payment process, transaction authorization by the card issuer is essential. This step involves the card issuer verifying that the cardholder has sufficient funds or credit available to cover the transaction amount. The issuer also checks for any fraud alerts or suspicious activity linked to the card, thus ensuring both the security of the transaction and the legitimacy of the cardholder’s identity.

While merchant approval, customer email confirmation, and physical card presence are relevant considerations in a broader context of card payments, they do not serve as the critical requirement for the transaction's completion. Merchant approval may facilitate the transaction by confirming that the merchant agrees to the payment, but without the issuer's authorization, the transaction cannot be processed. Customer email confirmation can improve communication but is not a standard requirement in the card payment process itself. Physical card presence can help to enhance security for card-not-present transactions, yet it is not always necessary, particularly for online or mobile transactions where card details are entered manually. Thus, the primary requirement remains the authorization by the card issuer.