Author
Payment systems expert and technology executive
Arif Ünal is a technology executive with more than 20 years of experience in banking, fintech and payment systems. He writes about card payments (issuing and acquiring), POS, ATM, e-money, FAST and Turkish payments regulation (BRSA and CBRT). He has held senior roles at Finagotech and managed payment systems and digital banking teams at Emlak Katılım, Vakıf Katılım and Türkiye Finans. He holds a B.Sc. in Industrial Engineering from Istanbul University and an M.Sc. in Management Information Systems from Marmara University.
976 articles
Merchant & POS
In the first post I explained what closed-loop payment systems are and how they differ from open-loop ones. Many of the replies I received boiled down to one question: how do these systems actually work behind the scenes once a QR code is scanned?
Payment Systems
The Hidden Side of the Payments World. The words a person working in the payment systems industry hears most over a career are probably Visa, Mastercard, POS, debit card, virtual POS, acquiring and card issuing. Frankly, my own career did not unfold very differently from that journey...
Payment System Institutions
One of the most important transformations in banking over the last few years has undoubtedly been remote customer onboarding. Individuals can now become bank customers within minutes without visiting a branch. Digital identity checks and contracts largely solved a long-standing problem...
E-commerce
AI agents are moving beyond answering questions to searching, deciding, and paying on behalf of users. This post explains Agentic Commerce and what it means for payment systems, digital wallets, e-money institutions, banks, and fintechs.
FAST
The Central Bank of the Republic of Turkey (CBRT) has implemented a significant limit increase in the FAST system. Under the regulation effective August 26, 2026, the FAST money transfer limit was raised from TRY 100,000 to TRY 300,000. The same increase also applies to Request to Pay...
Payment Systems
Contactless payment has greatly improved the user experience, yet its fixed transaction limit is a common complaint. Can this limit be managed dynamically per customer? This post covers the current situation, technical and regulatory requirements and the outlook.
Payment Systems
After switching to response code 70 for contactless limit-exceeded cases, we found that some overseas POS devices and acquirers did not handle it as expected. This post covers why the problem lies in the ecosystem and how to address it.
Credit Card
From the outside, Visa contactless looks simple, but once the limit is exceeded and PIN comes into play it gets deeper. Why do response codes 65 and 70 behave so differently on POS devices in different countries, such as the Netherlands and Saudi Arabia?
Payment Systems
One of the most notable recent developments in card payments is that contactless limits are no longer fixed and can be managed dynamically per customer. Mastercard and Visa are taking different but complementary approaches, and ISO 8583 may need to evolve with them.
EMV
The Visa EAS Server (Extended Access Service) is a server used in Visa’s authentication infrastructure. It was developed to run the cardholder authentication process securely between banks and the Visa network, particularly within Visa Secure (3-D Secure 2.x).
Payment Systems
In payment systems, an “appeal” is the process of objecting to the outcome of a transaction dispute. It is usually discussed alongside chargebacks, but it plays a critical role in interbank dispute resolution, when a party asks the card scheme to re-evaluate a concluded decision.
Payment Systems
An official BRSA letter to banks announced an update to the PIN-free contactless payment limit. From January 15, 2026, contactless payments of up to 2,500 TL can be made without entering a PIN, up from the current 1,500 TL.