Payment Gateway Integration in a Web or Mobile App

A Comprehensive Guide

ScienceSoft applies 34 years of experience in software integration and 18 years of experience in fintech to help businesses integrate payments in their web and mobile applications.

How to Integrate a Payment Gateway in the App - ScienceSoft
How to Integrate a Payment Gateway in the App - ScienceSoft

Payments Integration in a Web or Mobile App: Summary

Integration of payment functionality in a web or mobile application aims to help companies smoothly, quickly, and securely accept digital payments from customers.

Key project steps: Business needs analysis and requirements elicitation, integration conceptualization, project planning, tech stack selection, integration implementation and quality assurance, support and evolution of the integrated system.

Timelines: 2–5+ months, depending on the chosen approach to payments integration.

Cost: $20K–$100K to integrate a market-available payment gateway, $100K–$300K to build and integrate a custom payment gateway.

Team: a project manager, a business analyst, a solution architect, developers, a DevOps engineer, a QA engineer.

ScienceSoft provides all necessary talents to help our customers seamlessly integrate payment functionality in their web and mobile applications. We ensure prompt and high-quality integration with minimal disruption to internal business processes due to proven tech skills and multi-industry expertise of our team.

Apps That Will Benefit from Payments Integration

In web development since 1999 and in mobile development since 2005, ScienceSoft helps companies in 30+ industries design and build reliable web and mobile apps tailored to their business needs. Based on ScienceSoft’s experience, the following types of apps would benefit from the integrated payment functionality the most:

How to Integrate Payments in an Application

To enable payment functionality, your application should be integrated with an online payment gateway. Such software:

  • Connects to a web and/or mobile application that hosts a checkout page to collect purchasing details, personal information, and payment data (e.g., credit card data) provided by customers.
  • Encrypts sensitive data and transfers it securely to a payment processing system of an acquiring bank, an independent payment processing provider (e.g., PayPal, Stripe, Authorize.Net), or the company (in case of relying on in-house payment processing). The payment processing system verifies the customers’ personal and financial data and transmits transaction details to a payment processing network (e.g., a card network) that connects to the customer’s bank to finalize settlement.
  • Integrates with an accounting system to instantly communicate data on the successful payments and receive triggers to charge the recurring payments.

A Sample Architecture of Online Payment Gateway Integration by ScienceSoft

Architecture of Online Payment Gateway Integration - ScienceSoft

There are two main approaches to integrating a payment gateway with your application, each with its benefits and limitations. Here at ScienceSoft, we are ready to help you choose the optimal approach to meet your payment handling needs.

1. Integrating a market-available payment gateway

With this approach, you rely on a prebuilt payment gateway offered by a third-party payment processing provider (e.g., an acquiring bank, PayPal, Stripe, Authorize.Net) to handle customer payments. Such solutions offer ready-to-use APIs to facilitate and speed up integration with arbitrary apps and provide plug-and-play integrations with popular ecommerce platforms, accounting software products, analytical tools, etc.

Depending on the chosen payment gateway’s type – self-hosted or hosted – checkout can take place in your app or on a payment provider’s website. The former option provides a more consistent payment experience for customers and offers flexibility in terms of solution customization and branding. The latter option is more cost-effective as it doesn’t require maintaining a payment data storage infrastructure and achieving compliance with data security standards, such as PCI DSS. For more information, check our detailed comparison of hosted vs. non-hosted payment gateways.

Main benefit: A fast and easy way to integrate payments in the app with no investments in custom design of integration solutions and components (APIs, payment buttons, redirect scripts, webhooks, etc.).


  • The need to pay fees for the payment gateway provider’s services, including a one-time gateway setup fee, a monthly gateway fee, a merchant account setup fee, and a fee for each transaction processed.
  • Costly and lengthy integration with your legacy apps.
  • Customizing a prebuilt payment gateway to the company’s business-specific needs may be effort-consuming or impossible.

2. Building and integrating a custom payment gateway

With this approach, we develop an online payment gateway from scratch and build custom APIs to integrate the solution with your required business applications. Integration with an external payment processing system is enabled by the ready-made APIs that a payment processing provider (typically, an acquiring bank) provides.

Main benefits:

  • Minimized operational and security risks due to complete control over the checkout flow, transfer and storage of sensitive data.
  • Tailored functionality (support for all required payment methods, including cryptocurrency payments, recurring payments, refund processing) and required scalability, speed, and security of payment data processing to fully meet your unique needs.
  • Flexibility to evolve the payment gateway and add new features when needed.
  • Seamless integration with legacy web and mobile applications and corporate systems.
  • No fees for the payment gateway providers’ services.


  • The need to invest in custom solution design.
  • Responsibility for setting up and maintaining payment data storage infrastructure, as well as obtaining PCI DSS compliance, is fully on your side.

Note! As an alternative to custom payment gateway implementation, you may consider integrating your application with multiple prebuilt payment gateways. It could help overcome functional, non-functional, and geographical constraints of each particular ready-to-use solution. However, this option may appear economically unfeasible even for larger enterprises as it requires substantial investments in integration efforts and goes with large payment gateway license fees.

A Roadmap for Integrating Payments in an Application

A typical payments integration process with ScienceSoft looks as follows:


Business analysis and requirements elicitation


Conceptualization of payments integration in the app


Project planning


Choosing an integration tech stack


Payments integration implementation and quality assurance


After-launch support and evolution of the integrated system (optional)

Consider Professional Services to Integrate Payments in Your Application

In application integration since 1989 and in financial software development since 2005, ScienceSoft can help with:

Consulting on payments integration

Our consultants:

  • Help you conceptualize a payments integration solution.
  • Define the optimal integration patterns for a payment gateway.
  • Determine the integration architecture and tech stack.
  • Advise on an integrated system’s security.
  • Help comply with PCI DSS and other relevant standards.
  • Deliver a detailed payments integration roadmap for your app.

Payments integration

Our team takes over:

  • Payments integration solution conceptualization and feature mapping.
  • Integration architecture design.
  • Custom payment gateway development (if required).
  • Payment gateway integration with required systems and apps.
  • Quality assurance of the integration solution.
  • Payments integration launch and support.
  • Further evolution of the integration solution (optionally).

Why integrate payments in the application with ScienceSoft

  • Since 1989 in application integration services.
  • Since 2005 in financial software development.
  • Since 2003 in cybersecurity to ensure world-class protection of payments integration solutions.
  • Practical knowledge of 30+ industries, including ecommerce, BFSI, healthcare, telecoms, professional services.
  • Well-established Lean, Agile, and DevOps practices.
  • A quick project start (1–2 weeks) and frequent releases (every 2–3 weeks).
  • A mature quality management system and customer data security backed up by ISO 9001 and ISO 27001 certifications.
  • For the second straight year, ScienceSoft USA Corporation is listed among The Americas’ Fastest-Growing Companies by the Financial Times.

Typical Roles in ScienceSoft’s Payments Integration Teams

Project Manager

  • Plans the project scope (goals, timeline, budget).
  • Manages the project team.
  • Controls the integration progress.
  • Communicates with the stakeholders and reports the progress to them.

Business Analyst

  • Elicits, prioritizes, and documents the requirements for the payments integration solution.
  • Chooses an approach to payments integration (in collaboration with the solution architect).

Solution Architect

  • Defines a payments integration approach (in collaboration with the business analyst).
  • Architects the integration solution.
  • Designs frameworks and processes to support the implementation of an integration solution.


  • Write custom integration code (APIs, redirect scripts, etc.).
  • (in case of integrating a prebuilt payment gateway) Set up triggers and choose resulting actions for customer and payment data sharing.
  • Develop the UI and the back end of a custom payment gateway (if required).
  • Fix code issues on a QA engineer’s notices.

DevOps Engineer

  • Configures the infrastructure for the payments integration solution.
  • Automates integration processes by introducing a CI/CD pipeline.

QA Engineer

  • Designs and implements a test strategy, a test plan, and test cases for the payments integration solution.
  • Verifies the integration solution’s adherence to the quality standards defined in the project plan.

NB! ScienceSoft is ready to provide additional talents, for example, UX and UI designers to design a checkout page for your application.

Sourcing Models for Payments Integration in the App

ScienceSoft’s Success Stories of Payments Integration

Payments Integration for a Messaging App with 900M+ Active Users

Payments Integration for a Messaging App with 900M+ Active Users

ScienceSoft integrated the Viber billing portal with PayPal and a card network (Visa, MasterCard, American Express) to provide seamless payment experience for the Viber app users. The payment module architecture we designed enables fast and easy integration of new payment methods. Also, ScienceSoft’s team implemented a range of security algorithms to protect the integrated system against XSS and CSRF attacks.

Payments Integration in a Government Customer Portal

Payments Integration in a Government Customer Portal

ScienceSoft delivered an integration that connected a government customer portal with a banking module. Our team established integrations with international payment systems using CyberSource and Mastercard Payment Gateway Service to enable the customers to make convenient and secure payments.

A Telecom Provider’s Website Integration with PayPal

A Telecom Provider’s Website Integration with PayPal

ScienceSoft integrated a website of an international WiFi service provider with PayPal to enable easy customer payments for subscriptions.

ScienceSoft’s Tech Stack for Payments Integration in the Application

ScienceSoft’s team usually relies on the following tools and technologies to streamline payments integration into web and mobile apps and ensure high quality of an integration solution.

How Much Does It Cost to Integrate Payments in an App?

From ScienceSoft’s experience, each payments integration case is unique, so the cost factors vary for different customers. Below, we outline general factors that affect cost and duration of payments integration projects.

Integration cost factors

  • The chosen type of an online payment gateway (hosted or self-hosted), which defines the integration pattern.
  • The number and specifics of solutions to be integrated and the number of integration points.
  • (for a custom payment gateway) Solution complexity and requirements for the UX/UI of a checkout page.
  • The required modifications of the integrated apps, both on the technical level and on the app logic level.
  • The chosen sourcing model (in-house, outsourced).

Operational cost factors

  • Performance, availability, scalability, security requirements for the integrated system, which defines data processing and storage capacity and IT infrastructure security mechanisms.
  • (for a market-available payment gateway) Setup fees for a gateway and a merchant account.
  • (for a self-hosted payment gateway) The cost of maintaining PCI DSS compliance.
Pricing Information

Integration of a market-available payment gateway costs around $20K–$100K, while the implementation a custom payment gateway requires $100K–$300K in investments.

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About ScienceSoft

ScienceSoft is a global IT consulting and software development company headquartered in McKinney, Texas. We provide end-to-end application integration services to help companies integrate payment functionality in their web and mobile apps and seamlessly accept digital payments from customers. In our payments integration projects, we employ robust quality management and data security management systems backed up by ISO 9001 and ISO 27001 certification.