The merchant processing stability is very important. In contains the following aspects: approval rate, stable processing volume, bad cards number, customer complaints number.Online payment services do not only provide a processing gateway, it concludes many aspects in maintaining merchant account. The approval rate means the approved transactions proportion in total transactions. If the merchant’s approval rate is lower than 50%, half of the orders get declined, the approval rate is rather low. The declined reasons are varied. The reasons are subjected to bank, customer, merchant, technical reasons, network problems etc. First the bank has risk control system in order to prevent fraudulent transactions, potential risky transactions, bad cards transactions to protect the bank and the card holder in compliance with the credit card association policy and state law. For example: the stolen card, lost card, restricted card are rejected by bank system. Some cards are declined by the verification system but without providing details of the reason. Sometimes it is caused by the country limitation for cross-border transaction. Or the card has records which contains risky information in accordance with the bank regulation. Generally if the decline is from the customer issuing bank, the cardholder can directly contact the bank to ask approval for the transaction. If the bank declines account for large percentage of total transactions, in some extent, the merchant processing quality is not in high level. If the customer want to reverse the declined transactions, it is recommended the customer change another card to try again.