Cross-rail payment interoperability – connecting real-time payments systems

Catrine Rhenberg, Partner at Nurabal, analyses the potential of interoperability in the context of instant payments, looking at how scheme variations could impact developments in this direction. 

While account-to-account (A2A) payments can no longer be called a new payment trend, real-time payment (RTP) schemes have been proliferating rapidly across the globe in recent years, driven both by user demand and policy changes. Yet until now, most of this growth and success has been domestic, with use cases limited to country-specific applications within national borders. 

The relative maturity of SEPA Instant and legacy homegrown national schemes such as iDEAL, Swish, and others makes Europe a natural hub for cross-border innovation. Initiatives such as EuroPA and Wero are already making significant strides to connect Europe even beyond the unified SEPA Instant rails. Project Nexus is another big player in scheme interconnectivity, initiated in Asia. This progress is encouraging, but even more tantalising is imagining what can happen when connecting RTP schemes on a truly global scale. 

As technical interoperability becomes feasible, and the shift in attention goes from ‘Can we?’ to ‘When, how, and where should we?’, a new big question emerges.

RTP interoperability: where does it create genuine value and what obstacles remain underestimated?    

At first glance, remittances appear to be a clear contender for unified RTP, being one of the explicit priorities in terms of speed and cost improvements within the G20’s cross-border payments roadmap, adopted in 2020. However, in Q1 2024, the global average cost of sending a USD 200 remittance was about 6.35%, still well above the G20 target of 3% or less, and with many corridors exceeding the 5% ceiling. This gap between ambition and reality invites a deeper look at what can truly drive value in cross-border RTP interoperability and at potential use case misalignment. 

The Gulf states-South Asia corridors illustrate the last-mile paradox at scale. While Saudi Arabia is the largest source of remittances to Bangladesh, costs have risen significantly, according to recent reports, reaching 10.23% for a USD 200 payment in Q1 2025, higher than the G20's target. Although RTP interoperability could lower these costs, the overall value proposition diminishes when cash remains dominant in the recipient economy (e.g., Bangladesh, where approximately 72% of transaction value is cash-based). While cross-border RTP can efficiently deliver funds to bank accounts or mobile wallets, the final conversion to cash, particularly in rural areas where many remittance recipients live, remains the critical step. The speed in A2A transfers does not solve this issue. Their full benefits will be available when digital payments are adopted on a large scale domestically, a shift that is underway through initiatives like Bangladesh's National Payment Switch and Bangla QR. The question then becomes: ‘Can RTP remittances help accelerate this transition?’ 

Does the Germany-Turkey corridor present a more promising case for RTP interoperability? Turkey's FAST system has strong domestic adoption with millions of daily transactions. Until mid-2024, however, FAST's TRY 5,000 (USD 155) transaction limit was lower than the average remittance amount, requiring recipients to either split transactions or use alternative rails for larger transfers. This reflected FAST's optimisation for domestic micro-payments rather than cross-border family support. With the new, increased transaction limit (TRY 100,000) and Germany-Turkey remittance costs still high, the corridor presents clearer cost-saving potential. Realising these savings requires not just technical connectivity, but also ensuring FAST's merchant network extends meaningfully beyond metropolitan hubs to smaller cities (where many remittance recipients live), supported by the new transaction limits. 

The EU-India corridor may offer one of the strongest cases for RTP interoperability, with clear utility for the recipients. Crucially, India’s UPI merchant network, with over 50 million acceptance points and deep penetration in both urban and rural areas, enables recipients to immediately deploy received funds for daily needs (rent, school, food, etc.) without reverting to cash. This ecosystem maturity extends the technical possibility of interoperability into genuine value delivery. 

The above examples challenge an implicit assumption: that technical connectivity creates equivalent value across any corridor. In practice, RTP schemes reflect distinct domestic priorities. This domestic focus can, in turn, give us an indication of which cross-border collaborations will flourish and which will falter, despite seamless technical integration.

Domestic RTP scheme variations – aspects to consider for instant payments interoperability

Let’s look at some of the different paths adopted by major RTP schemes:

• India's UPI was designed for merchant payments and micro-transactions, with QR code ubiquity and an average transaction value of approximately USD 20.
• Brazil's Pix integrated bill payment rails from the start, making it as easy and natural to pay utility bills as a transfer to a friend.
• Europe's SEPA Instant emerged from a banking-led consortium optimising for interbank transfers and ecommerce checkout.
• Turkey's FAST prioritised P2P payments with a mobile-first design. 

These scheme variations do not just point to technical differences; they represent fundamentally distinct ideas of what instant payments should accomplish within their domestic economies. 

So, what happens when schemes designed for different purposes decide to connect? There is a risk of friction, not at the technical layer, but at the operational and commercial layers. A concrete example: UPI's architecture assumes high-frequency, low-value transactions with minimal pre-funding requirements for payment service providers (PSPs). Conversely, SEPA Instant was built for lower-frequency, higher-value transactions, with defined pre-funding and settlement arrangements between banks. Therefore, connecting these schemes requires more than message translation; it demands reconciling conflicting assumptions about liquidity management, risk tolerance, and transaction economics. That is not to say it cannot be done successfully, but attention must be given to the details of the use cases.

RTP interoperability in ecommerce – challenges and opportunities

Beyond remittances, cross-border ecommerce represents a compelling interoperability use case, yet it can also expose design mismatches. Consider EU consumers purchasing from Turkish merchants on platforms like Trendyol, or UK consumers buying from EU retailers: the merchant needs payment certainty to ship goods, the consumer expects dispute resolution rights, and the platform wants low cart abandonment. 

SEPA Instant was designed with ecommerce in mind. Transactions were previously capped at EUR 100,000, but following the 2025 rulebook, the EPC is no longer enforcing a scheme‑wide maximum amount, leaving PSPs to set their own limits. Irrevocable payment confirmation enables immediate order processing. Turkey's FAST, with its initial limits, served domestic ecommerce adequately but created friction for hypothetical cross-border purchases. A USD 200 order from Germany would have required either transaction splitting, creating operational complexity and potential failure points, or routing through traditional rails, defeating the purpose of interoperability. 

But even when transaction limits are no longer an issue, ecommerce interoperability requires aligning not just payment rails but consumer protection frameworks. EU consumers expect PSD2's strong customer authentication and chargeback rights. If a connected scheme lacks equivalent protections, who bears the fraud risk? Currently, there is no clear, unified answer. 

The UK-EU corridor illustrates this well. Post-Brexit, UK merchants lost SEPA access, which forced them towards card networks (higher fees) or international wire transfers (slower settlement). Connecting the UK Faster Payments System to SEPA Instant could reduce costs from 2-3% (cards) to well under 1%, benefiting millions of transactions. But achieving this requires harmonising ISO 20022 messages, as well as reconciling the UK's Payment Systems Regulator management of fraud reimbursement with EU member states' individual liability frameworks. Regulatory interoperability remains the biggest barrier to success.

RTP interoperability in B2B cross-border payments – commercial requirements

The USD 68 trillion B2B cross-border payments market dwarves remittances, yet most RTP schemes were not architected with B2B priorities in mind. Corporate treasurers require rich remittance data (e.g., invoice numbers, purchase order references), exception handling workflows, and integration with accounting systems. Consumer-oriented RTP schemes often support minimal message fields, optimising for speed over data richness. 

Transaction limits present another barrier. While the EPC no longer enforces a maximum amount, PSPs setting individual limits creates potential uncertainty for B2B transactions, and could still exclude larger invoices common in manufacturing, wholesale, or construction. Turkey's FAST caps merchant payments at TRY 250,000 (roughly USD 5,800), which removes the uncertainty but limits certain types of transactions. 

B2B payments also assume different risk tolerances than consumer transactions. Instant and irrevocable settlement, a key consumer feature, becomes a bug for corporations that need dispute windows, conditional payment releases, or escrow functionality. Supply chain finance products require payments to be held, released conditionally, or even reversed. RTP's essence conflicts with these commercial requirements. 

So, where do clear B2B opportunities exist? In smaller, high-frequency transactions: restaurant chains paying suppliers daily, logistics companies settling shipping fees, or marketplace platforms paying sellers. These 'B2B2C' transactions (frequent, moderate-value, and with real benefit from instant settlement) represent a sweet spot where RTP interoperability could displace expensive card-based commercial programmes. However, capturing this market does require some modifications to meet B2B-specific features, such as enhanced data fields, bulk payment support, and corporate onboarding processes. 

The pattern that emerges from these use cases confirms that interoperability creates value not by connecting any two schemes, but by connecting schemes that truly align across parameters such as design philosophy, transaction profiles, and operational assumptions. 

This suggests a more strategic approach to prioritising interoperability investment. Evaluating corridors must be done not just by looking at transaction volume or remittance costs, but by judging the compatibility of the underlying schemes for specific use cases. A remittance corridor between consumer-optimised schemes may deliver limited value compared to an ecommerce corridor connecting schemes built for merchant acceptance, even if the remittance volumes appear larger on paper.

Final thoughts

Despite these complexities, the momentum towards cross-rail RTP interoperability is undeniable, and as seen by the number of requests reaching Nurabal, the appetite is real! The technical building blocks are maturing: ISO 20022 adoption is widespread, while Project Nexus and regulatory frameworks (like PSD3) are establishing clearer interoperability expectations. 

The value proposition, when conditions align, is transformative:

• For remittance recipients in digitally mature markets, instant cross-border transfers at near-zero cost could redirect billions of dollars annually from intermediary fees to families and communities.
• For cross-border ecommerce, seamless A2A payments could reduce merchant costs significantly, while improving conversion rates through familiar payment experiences.
• For B2B commerce, particularly in high-frequency, moderate-value transactions, the potential, due to the size of the market, is immense. 

The path forward requires moving beyond the assumption that connectivity equals value. Success will come from strategic corridor-by-corridor approaches that prioritise ecosystem compatibility over universal connection. It demands an honest assessment of use case alignment and requires industry coordination on the essential work of fraud frameworks, liability standards, and regulatory harmonisation.

The question is not, in my opinion, whether cross-rail RTP interoperability will happen; it is ‘Where will it first create the most value?’ and ‘Who are the stakeholders that will shape its evolution?’. 

About the author

Catrine Rhenberg is a payments expert and Partner at Nurabal, advising banks and fintechs on RTP solutions, cross-border transfers, and more. She previously held senior roles at PayPal and Trustly, among others, leading partnerships and ecosystem initiatives across Europe and beyond. Drawing on years of hands-on experience in digital payments, Catrine helps clients turn complex payment challenges into simple, reliable experiences for consumers and businesses in multiple markets.

 

 

About Nurabal

Nurabal is a niche payments consulting firm specialising in RTP schemes and cross-border instant payment connectivity. Headquartered in Singapore, Nurabal partners with global banks, fintechs, and payment infrastructures to design, optimise, and scale RTP-enabled propositions. With deep scheme and market expertise, Nurabal helps clients navigate technical interoperability, liquidity, and operating models to unlock new value from instant payments across multiple regions and use cases.