Payment gateway integration services connect websites and apps to the systems that process card transactions. Different processors use different protocols. Settlement files arrive in varying formats. Chargeback workflows differ by bank. Getting these connections right requires experience with the specific quirks of each payment system.
The companies listed below specialize in this work. They have built integrations for platforms processing millions of transactions. They understand authorization routing, settlement reconciliation, and compliance across multiple geographies.
1. ELEKS
ELEKS is a global software engineering company that was founded in 1991. The firm provides full-cycle development for banks, investment firms, insurance companies, payment providers, and asset management organizations.
ELEKS specializes in secure, data-driven systems for transactions, fraud prevention, risk modeling, analytics, and digital banking transformation. Their core capabilities include low-latency trading systems, machine learning-based fraud detection, risk modeling tools, and high-frequency data processing platforms.
The firm has deep expertise in real-time data processing and fraud detection. They build investment platforms and portfolio management systems for financial institutions.
Core strengths: Fraud detection, real-time data processing, investment platforms
Key markets: Banks, investment firms, insurance companies, payment providers
2. ScienceSoft
ScienceSoft is a software consulting and development company founded in 1989. The firm employs 750+ IT professionals and operates nine principal architects with 15–25+ years of experience each.
The company has 21 years of experience in payment gateway API development. Their payment gateway integration services cover hosted, direct post, self-hosted white-label, and custom gateway implementations. ScienceSoft follows a structured integration process: analysis of the as-is situation, requirements engineering, project planning, architecture design, tech stack selection, implementation, and testing.
ScienceSoft has delivered a PA-DSS-compliant payment gateway with 3D Secure authentication. The firm also developed secure crypto payment API integration for a leading digital entertainment platform and built a mobile payment app for 18 million e-wallet users.
The company holds ISO 9001 certification for quality management and ISO 27001 for security management. Their payment system implementation services typically take 2–5+ months and cost $20,000–$100,000, depending on complexity.
Integration timeline: 2–5+ months, depending on integration complexity
Cost range: $20,000–$100,000, depending on integration complexity
Certifications: ISO 9001 for quality management and ISO 27001 for security management
3. SPD Technology
SPD Technology is a fintech software development company with 18+ years of experience building payment platforms and PSD2/PCI DSS-compliant fintech products for companies in the UK, US, and EU. Founded in 2006, the firm operates as a product engineering partner, not an outsourcing vendor.
The company holds certified Adyen Implementation Partner status. Engineers build PSP abstraction layers that treat processors as interchangeable components. This approach allows clients to switch providers without rewriting core logic.
For Poynt (now HP Commerce), SPD Technology built a full-cycle payment processor integration covering authorization, settlement, and third-party integrations. That platform processes 140 million transactions each month. The integration work included connecting to multiple payment partners while maintaining transaction success rates.
The company also delivered an aggregated merchant portal for BlackHawk Network. The portal automated merchant payment integration through KYC workflows and reduced setup time by 7x.
SPD Technology serves as a payment platform integration company for fintech scale-ups and digital payment companies. Their eCommerce payment gateway integration work spans direct post, hosted, and integrated methods depending on what fits the client’s infrastructure.
Integration expertise: 20+ payment systems integrated for a single high-scale marketplace
Security focus: Tokenization, encryption, fraud prevention implementation across all integration projects
4. Geniusee
Geniusee is a custom software development company founded in 2017. The firm has 220+ specialists on board, including developers, AI experts, designers, QA, and DevOps professionals.
The company connects business needs with rapid MVPs and modern cloud solutions. Projects run with transparent sprints, secure pipelines, and strong accountability. Geniusee can ramp up a dedicated team within 2–4 weeks.
The firm handles core banking and ledger engineering, payment processing, open banking integrations, and white-label lending platforms. Clients receive full IP ownership and documentation. Geniusee holds AWS Certified Partner status and follows ISO-certified processes.
Payment API integration at Geniusee connects secure gateways and banking APIs for BNPL platforms. Their payment gateway API development includes secure RESTful, GraphQL, and gRPC interfaces that bridge frontend apps with ERP, CRM, and payment systems.
Integration expertise: Multi-channel payment solutions, open banking APIs, secure RESTful/GraphQL interfaces, cross-platform UX
Key capabilities: Custom gateway engineering, BNPL platforms, payment API connections, white-label lending
Comparison Table
Some firms excel at specific integration models while others handle the full stack. Here is how these four compare on the metrics that matter most.
| Feature | ELEKS | ScienceSoft | SPD Technology | Geniusee |
| Founded | 1991 | 1989 | 2006 | 2017 |
| Team size | 2,000+ | 750+ | 400+ | 220+ |
| Key markets | Global | US, EU, UAE | UK, US, EU | UK, EU |
| Integration approach | Real-time data, fraud detection | Hosted, direct post, white-label, custom | Proprietary framework, PSP abstraction layers | BNPL, open banking, cross-platform |
| Compliance | PCI DSS, GDPR, SOC 2 | PCI DSS, 3D Secure, GDPR, SOX | PCI DSS, GDPR, PSD2, KYC, SOC 2 | PCI DSS, KYC, AML, PSD2 |
Each firm’s integration approach reveals how they work. Long-standing companies bring stability and process, newer ones offer flexibility and faster turnarounds. The right match depends on your transaction volume, processor requirements, and compliance obligations.
What Integration Partners Often Miss
- Payment system implementation services often overlook settlement timing. Files arrive at 3 AM. Your system expects them at midnight. That mismatch creates reconciliation nightmares. Many integration firms don’t ask about settlement timing until late in the project.
- Currency conversion is another blind spot. Some processors calculate FX rates at authorization. Others do it at settlement. The difference affects merchant payouts. Integration partners who don’t flag this early leave clients with accounting problems later.
- Error codes matter more than most firms admit. One processor returns code 05 for insufficient funds. Another uses the same code for expired cards. Mapping these differences requires reading the fine print. Many integration teams skip this step and write generic error handling.
- Chargeback workflows vary by region. European banks have different dispute timelines than US banks. Integration partners who assume uniform processes create systems that fail compliance checks.
- Ask about partial approvals too. Some networks allow splitting a declined $100 purchase into two $50 approvals. Most integration firms don’t support this feature. Merchants lose sales because the gateway says no instead of asking the issuer for a partial yes.
The best partners map these edge cases before writing code. They test settlement timing with real batch files from each processor. They verify error code mappings in sandbox environments. They simulate chargeback scenarios across multiple regions.
Conclusions
Payment gateway integration requires technical skill and practical experience. The right partner should have worked with the specific processors your business needs. They should understand the compliance requirements that apply to your market. And they should be able to handle the transaction volumes you expect.
SPD Technology stands out for its certified Adyen partnership and proprietary integration framework. ScienceSoft offers the deepest payment gateway API development experience with 21 years in the space. ELEKS brings strong fraud detection and high-frequency processing capabilities. Geniusee provides rapid MVPs and transparent development sprints.
Each firm on this list has delivered payment processor integration projects at scale. The choice comes down to your specific requirements, geography, and transaction volume.