How to Build a Payment Processing App for an E-commerce Store

How to Build a Payment Processing App for an E-commerce Store

06 September 2023 • 17 min read

In online shopping, payment processing apps have become the beating heart of e-commerce stores. It's important to build a payment processing app that facilitates seamless transactions and improves your customers' shopping journey. This app connects customers with their purchases, making it a vital part of their shopping experience.

With over nine years in software development, Softermii has earned a reputation for making secure payment systems. One of our flagship projects, Expedipay, exemplifies our proficiency in this arena. This article outlines the main features, development process, and cost of payment processing apps. We also provide you with case studies of payment processing apps and cover our experience with Expedipay development.

Must-Have Features of Payment Processing Apps

As an e-commerce business owner, it's pivotal to invest in a robust payment processing solution that meets the expectations of your clientele. The following features allow you to provide a seamless user experience and foster trust and loyalty among consumers.

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User-Friendly Interface

Your payment app should offer a clean, intuitive interface, so users can easily navigate the payment process.

Multiple Payment Options

Include popular payment gateways like credit/debit cards, bank transfers, digital wallets, and even cryptocurrencies. They provide flexibility for users with varying payment preferences.

Build a payment processing app

Real-Time Transaction Monitoring

With this feature, you can see transactions happening right now. It helps in identifying and addressing any anomalies or fraudulent activities.

End-to-End Encryption

It protects customers' sensitive information and safeguards it against potential breaches.

Multi-Currency Support

For e-commerce stores serving a global audience, using multi-currency support is important. It lets customers see prices and pay in their local currency, enhancing their shopping experience.

Develop a payment processing-app

Quick Checkout Options

Features like one-click checkout or the ability to store card details (with the user's consent) can speed up the payment process. Also, they can reduce cart abandonment rates.

Payment processing app development

Mobile Optimization

With a surge in mobile shopping, ensuring that your payment app is mobile-friendly is indispensable. It includes fast loading times on a phone, touch-friendly buttons, and mobile wallet integrations.

Build a payment app for an e-commerce store

Create a payment app for an e-commerce store

Payment Analytics

Insights into payment trends, peak transaction times, and 'successful vs failed transactions' tracking can assist businesses in refining their strategies and enhancing the user experience.

Developing a payment app for an e-commerce store

Fraud Detection and Risk Management

AI and machine learning can help your app to identify suspicious activities and flag them for review. It minimizes chargebacks and potential fraud, enhancing greater trust in customers.

Recurring Billing and Subscription Management

If you offer subscription services, set up a system that automatically bills customers at set intervals and sends an invoice afterward. It should include managing subscription upgrades, downgrades, or cancellations.

Create a payment processing app

24/7 Customer Support

Account offering round-the-clock customer support to address any queries or problems quickly.

Develop a payment app for an e-commerce store

Tax and Compliance Management

You need to create online payment platform that can handle tax calculations based on the user's location. It should also ensure that the business remains compliant with global tax regulations.

Payment Processing App Development Process

Developing a payment app for an e-commerce store requires a meticulous approach and attention to detail. Here's a step-by-step guide through the development process:

Planning, Ideation, and Discovery

Evaluate the specific requirements of your e-commerce store. For instance, if your store caters to a global audience, it needs multi-currency support. Research competitors and identify gaps in their payment processing approaches that you can capitalize on. Decide on the technologies and platforms that will form the foundation of your app.

UI/UX Design

During this stage, a basic structure of the app is created, outlining the positions of the essential features. Then you get a clickable prototype to simulate the user journey. It allows you to make iterative changes before actual development begins. Afterward, designers incorporate brand colors, typography, and other design elements to create a visually appealing interface.


The development team works on the interface that users will interact with. They ensure it's intuitive, responsive, and consistent across different devices. They also integrate with payment gateways, ensure secure encryption of sensitive data, and set up servers to handle transactions.

Testing and Launch

Unit testing tests individual components of the app to ensure they function correctly in isolation. Integration testing checks if all the components work seamlessly when integrated. Consider user acceptance testing to gather feedback from potential users and make any necessary tweaks. After all of that, the app can be launched. It's important to measure its performance and gather user feedback in real time.

Technical Documentation

It is crucial for future development phases or if other developers need to work on the app. The documentation includes details about the architecture, codebase explanations, API references, etc.

Cost to Build a Payment Processing App

Now you know the stages of developing a payment app for an e-commerce store. However, it's crucial to grasp the investment required. The table below summarizes the development stages, estimated costs, and development time.

Payment Processing App Development Cost

Development Stages




Planning, Ideation, and Discovery

280 hours

$11 200


UI/UX Design

200 hours

$6 000 



640 hours

$25 600


Testing and Launch

240 hours

$9 600


Technical Documentation

40 hours

$1 600


1 400 hours (approximately 9 months) 

$54 000 

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Note that these are the approximate costs, and the actual ones may vary. Drop us a line, and we will calculate a detailed plan based on your needs. 

Also, the cost to create a payment app for an e-commerce store can vary widely based on numerous factors. It's essential to understand these determinants to budget effectively and ensure a return on investment.

Scope and Complexity

A basic app with a simple payment gateway might be relatively inexpensive. Yet, a multifaceted app with numerous payment options, currency conversions, and advanced fraud detection can drive up costs. Tailoring the app to meet specific needs or incorporating proprietary algorithms adds complexity and cost.

UI/UX Design

Using off-the-shelf design templates is cheaper, but a custom UI/UX design that enhances user experience and matches your brand can be more pricey. A seamless user journey requires meticulous design and iteration, which can be more costly.

Development Team

Hiring an in-house team gives you better control over the project, but sometimes hiring freelancers or outsourcing is cheaper. Still, senior developers or agencies with a rich portfolio often ensure a smoother development process and better quality output. As usual, dedicated team members have previously worked together on different projects. Thus, they have higher expertise and can ensure a more seamless work process.

Maintenance & Upgrades

After your app is up and running, you'll need to spend costs on post-launch support. It includes bug fixes, performance optimization, and addressing user feedback. As the e-commerce landscape evolves, introducing new features will have associated costs.

Additional Costs

Payment gateways, security certifications, or third-party services usually have associated licensing fees or subscription costs. If the app has intricate features or is built for enterprise-level operations, training the staff can also introduce additional costs.

Case Studies and Examples: Real-World Implementations of Payment Processing Apps

Real-world implementations of payment processing apps provide valuable insights into their functionality, adaptability, and effectiveness. Here are a few examples showing how e-commerce stores have adopted these apps.

Stripe for Shopify 

Shopify's partnership with Stripe has been one of the most notable collaborations in the e-commerce world. This integration has allowed Shopify merchants to handle transactions seamlessly across many countries. With its transparent fee structure, extensive currency support, and robust fraud prevention mechanisms, the Stripe solution within Shopify has set a gold standard for e-commerce payment systems.

Adyen for eBay

Moving away from its long-time partnership with PayPal, eBay chose Adyen as its primary payment processing partner to improve its user experience. This shift aimed to provide customers with a more integrated checkout process. Adyen's infrastructure enabled eBay to deliver a smoother and more straightforward purchasing journey.

Klarna for ASOS and other Retailers

Klarna, a leading European payment service provider, offers a 'buy now, pay later' method. It has gained significant traction as modern consumers benefit from these flexible payment options. The ASOS merchant integrated Klarna to cater to its younger audience, who prefer paying in installments or after receiving the products. Shoppers found this payment process more aligned with their financial preferences. Thus, the integration led to an increase in conversion rates and a broader customer base. 

How to build a payment processing app

Softermii's Experience in Payment Processing App Development

Softermii stands where technology and innovation come together, providing advanced digital solutions for important business needs. With a proven track record in the fintech realm, we create secure and user-friendly payment systems.

One such flagship project that underscores our proficiency in this arena is Expedipay. We designed a platform with secure and unfettered access to essential financial services. Expedipay ensures that financial services are within everyone's reach, regardless of geographical or infrastructural constraints.

Payment processing app cost

At the heart of Expedipay lies its primary feature: a robust P2P money transfer mechanism. It allows users to execute money transfers swiftly without compromising security. We aimed to build a p2p payment app with eKYC integration to ensure a fraud-resistant authentication process. Our team also introduced the feature to add card lists to the Mobile Wallet, which empowers users with rapid payment capabilities.

The Expedipay project shows our commitment to delivering solutions that resonate with contemporary challenges. We not only address the immediate problem but also envision the broader impact. Our digital solutions are aimed at making finance more inclusive and empowering for everyone.

Final Notes

It's essential to build a payment app for an e-commerce store for seamless transactions and a positive customer experience. Real-world examples such as Shopify and Stripe, eBay and Adyen, and ASOS with Klarna demonstrate the impact of payment processing apps. The Expedipay project showcases our ability to tackle contemporary challenges in fintech.

Building such an app requires a profound understanding of technology and user needs. Softermii is ready to guide you in creating an effective app tailored to your needs. Get in touch with our team to transform your e-commerce store with a seamless payment experience.

Frequently Asked Questions

What is the typical technology stack to develop a payment processing app?

A technology stack often includes programming languages, frameworks, databases, and APIs. Common choices include languages like Python, Ruby on Rails, or Java, secure APIs for payment gateways, and front-end frameworks for user interfaces. A development company like Softermii can fully manage your project's technical aspects. It lets you concentrate on your business while our experts handle the app's technical implementation.

What is the time and cost investment for developing a payment processing app?

The timeline and cost for building a payment processing app vary based on design complexity, feature requirements, personalization, and platform choices. The development process spans a minimum of nine months, with costs ranging from around $50,000. Note that your needs and project objectives influence the final expenses and development duration.

How do I ensure the security of payment transactions and customer data?

Ensuring security in payment processing apps is paramount. Here are key steps to enhance security:

  • SSL Certification. Use SSL encryption for all data transfers, ensuring that sensitive information is encrypted during transmission.
  • PCI DSS Compliance. Adhere to PCI DSS guidelines to handle credit card information safely.
  • Tokenization. Use it to replace sensitive data with unique symbols, ensuring that actual card or bank details aren't stored on your servers.
  • Multi-factor Authentication. Introduce multi-factor authentication for transactions, adding an extra layer of security.
  • Regular Audits. Conduct regular security audits and vulnerability assessments to detect and rectify potential weaknesses.
  • Fraud Detection Tools. Implement advanced tools to identify and prevent suspicious transactions in real time.

Are there any legal considerations when building a payment processing app?

Yes, there are several legal considerations to keep in mind when building a payment processing app:

  • Regulatory Compliance. Different countries have specific regulations related to electronic transactions and data privacy. In the U.S., for example, one must comply with the PCI DSS. In Europe, there's the GDPR law concerning data protection and privacy.
  • AML and KYC Policies. Ensure that your app has mechanisms to prevent money laundering and verifies the identity of users to mitigate fraud.
  • Consumer Protection Laws. They protect consumers' rights, especially regarding refunds, chargebacks, and disputes.
  • Licensing. Depending on the region, you might need certain licenses to operate as a payment processor.

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