The Complete Guide to Payment Gateway Integration

Online payment gateway integration attempts to make it easier for e-commerce businesses to receive digital payments from clients. Between an e-commerce application and one or more payment processing systems, an online payment gateway ensures the immediate and safe transfer of a customer’s personal and payment information. 

Here are the key steps to payment gateway integration: 

– Choosing a payment gateway provider

– Setting up an account

– Getting API credentials

– Integrating the gateway

– Testing the integration

– Going live

Timeline: starting from 2 weeks and up to several months, depending on the project goals.

Cost: starting from $5K, depending on the integration complexity.

Sloboda Studio can offer all the expertise required to cover the end-to-end integration of an online payment gateway and aids businesses in reducing the time and expense of integration projects.

What is a Payment Gateway? 

A payment gateway is a mechanism that reads and transfers payment information from a customer to a merchant’s bank account. A merchant account is a dedicated bank record used to deposit money resulting from online customer purchases. It acts as a hub to facilitate the flow of funds between customers and merchants. Various security measures and encryptions are implemented to ensure transaction data safety. 

Payment gateways can perform the following types of transactions:

• Authorization – This type of transaction is done to check if the purchasers hand enough money in their account to pay for the goods or services. Here, there is no actual money transfer. 
• Capture – Here, the authorized payment is processed, which leads to the transfer of funds. 
• Sale – This is a combination of capture transactions and authorizations. First, the cardholder is authorized. Then, the money may or may not be captured. 
• Refund – This occurs when an order is canceled, and the business has to make a refund to the customer. 
• Void – It is similar to a refund but happens when the funds are not captured. 

Online Payment Market Overview and Forecast for 2027

You may think that cashless payment methods are a recent innovation. You will be shocked to learn it originated in the second half of the 12th century. Italian merchants used notes called “Lettres de foire” instead of coins or precious metals to make transactions. The merchants used this method for security and logistic reasons. A cart full of coins and precious metal not only attracted unwanted attention but could be a pain to transport over long distances. Forward to the 21st century, and the idea remains stagnant. However, technology and financial exchange methods have changed. 

Cashless checkout methods are definitely taking over the world. 

Over 80% of purchases that occurred in the US in 2022 were done with methods other than cash. The total transaction value of online payments is expected to show an annual growth rate (CAGR 2022-2027) of 12.31% resulting in a projected total amount of US$15.17tn by 2027. 
In 2021, over half of global e-commerce transactions were performed using mobile and digital wallets. This share is set to increase to more than 53 percent in 2025.

Payment methods in 2021, with a forecast for 2025, Source

Payment Processing Flow

The online processing infrastructure is much more complicated than what meets the eye. All customers see is the checkout page and some notifications from their bank apps. However, that’s just the tip of the iceberg. 

In reality, payment processing involves many other back-end processes, multiple financial institutions, tools, and verifications needed to complete the purchase. 

For one of our projects, Uniting Health, our development team had to implement ACH payment. It is a specific bank-to-bank type used in the US. We had decided not to outsource ACH implementation. So, our team had to perform it manually. For such implementation, we created our own verification system. Then, implemented both credit card and ACH payment methods through Stripe.

How It Happens

Here’s how the payment processing happens. Note that all these steps occur in just a few seconds after the customer presses the purchase button:

• Customer. The customer clicks on the “Purchase” button and enters all the details. This data is encrypted and transferred to the merchant’s web server through an SLL connection. 
• Merchant and payment gateway. The merchant sends data received to the gateway through an encrypted SSL (Secure Sockets Layer) channel. SSL is a protocol for establishing authenticated and encrypted links between networked computers. Here, tokens are stored instead of credit card numbers for security purposes. If any data has to be stored in the gateway, it is kept in secure storage. 
• Payment processor. From the gateway, the data is sent to payment processors. These are third-party companies that provide payment processing services. They help to transfer data between the payment gateway and the merchant. At this point, the payment processor sends the transaction to the card network (Mastercard, Visa, etc.). 
• Card network. The card network is responsible for verifying transaction data and sending it to the bank that issued the consumer’s credit/debit card. 
• Issuer bank. The consumer’s bank then approves or denies the authorization request. A unique code containing transaction status or error details is then sent back to the processor by the customer’s bank.
• Payment gateway. The transaction status is then sent back to the payment gateway, which is then transferred to the website.
• Customer and issuing bank. The purchaser then receives a notification from the bank about the transaction status through the app or SMS. 
• Issuer bank. It takes about two days for the customer’s bank to transfer the funds to the merchant’s bank.

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Payment Gateway Integration: Every Type Explained

There are multiple types of online payment gateways which have unique functionality. All of them need a different integration approach. For example, there are ones that use a redirect to the third party and those that allow payments on the website:

Hosted Payment Gateway

When customers press the purchase button on an eCommerce checkout page, they are redirected to the gateway provider’s platform to finalize the payment. Once that is done, the customer is redirected back to the eCommerce website. This means that all the sensitive data storage and transaction processing is done at the provider’s end. 

This method makes it easy and fast to provide digital payments without direct integration with the payment processing network. Also, your business does not have to worry about the safety of sensitive data or comply with security requirements. However, your business will have no control over the payment gateway.

Direct Post Payment Gateway

Here, the business uses a third-party payment gateway. However, customers are not redirected to another site to complete the payment. Once the purchase button is clicked, payment and customer data are sent from the website’s back-end. Then, it goes to the gateway’s server for processing and storage. 

Customers are not redirected to another website. This makes the checkout faster and more user-friendly. Also, your business is not required to retain or handle customer financial information. So there is no need to maintain PCI DSS compliance. However, your company will be limited in how it can customize payment options and checkout experiences. 

While working on the Cleaning Marketplace project, we had to implement and integrate a payment gateway system.

The client’s business model includes a payment that takes place after the cleaning is completed. So issues with conducting payments used to occur (for example, due to the customer’s insufficient funds). Plus, a cleaner’s payout happens in the same time frame as the customer being charged.

The solution to this problem was to provide a notification about a payment failure. Once fails, it triggers an email notification about the unpaid cleaning. This notification invites the customer to log into the dashboard (link in the email redirecting the user to the PTH dashboard) and click on the “PAY NOW” button. 

In the dashboard, the customer can see the reason for the transaction error. We used the Stripe system to define the types of such errors. 

Self-Hosted White-Label Payment Gateway

As the name suggests, this is a white-label payment gateway solution that can be bought ready-made. It can then be integrated into the business’s website using APIs. The checkout process occurs with the website. There are no redirects. 

It gives businesses much control over the processing and storing the customer-sensitive data and payment data. However, there are also downsides to this type of payment gateway. Your company processes and stores all the data. It needs to pay close attention to security details and strictly comply with PCI DSS. Also, it becomes significantly time-consuming and costly to integrate a white-label payment gateway with older apps. To do this, lots of customization is needed. 

Non-Hosted Custom Payment Gateway

This payment gateway solution is built from scratch specifically for your business’s needs. It integrates directly into your website or app using custom APIs. Also, the checkout process occurs within the app. It gives your company complete control over the payment and can integrate seamlessly with legacy systems. Also, you don’t need to pay fees for intermediary services. Since you don’t depend on third-party online transaction processors, the security and operational risks are reduced. 

Even with all the benefits, this type of payment gateway solution comes with some flaws. Needing to build from scratch can be time-consuming and requires lots of resources. Furthermore, your business is responsible for maintaining and supporting the payment processing infrastructure. It also needs to ensure complete compliance with PCI DSS. 

How to Integrate a Payment Gateway

Integrating a payment gateway depends on the specific payment gateway service provider you want to use, as each provider may have different methods and requirements for integration. However, here are the general steps involved in integrating a payment gateway:

Choosing a Payment Gateway Provider

When you need to pick a new payment gateway provider, you can find one among plenty on the market. Each service provider has specific features, pricing, and integrations. So, before considering a specific provider, you should check on needs, money, and goals. 

Some businesses may require a payment gateway provider who takes multiple currencies or has sophisticated fraud detection capabilities. Others may prefer website incorporation or payment acceptance via mobile devices. Furthermore, the provider’s costs, including any startup fees, transaction fees, and monthly fees, should be investigated.

Setting up an Account

After deciding on a payment gateway provider that suits your business needs, the next step is to set up an account. Here you’ll need to provide some basic info about your business — name, address, phone number, tax information, etc. There’s also a possibility that some providers may ask you about bank details, website address, or service details.

Once you set and verify your data, you can start integrating the payment gateway into your website or mobile app and start accepting payments. Don’t forget to follow the provider’s guidelines and best practices to make sure that your transactions are secure and compliant with industry standards.

Getting API Credentials

API credentials are like keys that let your website or app talk securely to the payment gateway when processing payments. You generate them in your provider’s developer portal, and they’re unique to your record. Then you add them to your payment processing system to let customers pay securely on your website or app. Just be sure to follow the provider’s instructions, so you keep things safe and legit.

Integrating the Payment Gateway

After getting your API credentials, the next step is to add a payment form or button to your website or app. When customers click it, they’re redirected to the payment gateway’s website to complete the payment. You might be able to customize the form and offer different payment options too. Just make sure the payment page is safe and easy to use for customers. 

Note: Following the payment gateway provider’s instructions is crucial for secure and compliant payment processing.

Testing the Payment Integration

Test your payment gateway as you add it to your website or app. Run your first payment transactions yourself to make sure that everything works as it should. This means that you need to check all payment details are correct and see if you get notifications and receive payments on time. It’s important to test various payment scenarios and use the payment gateway’s sandbox environment for testing. This will help you make sure that payments are processed safely and following the rules. Testing helps you fix any issues before they impact your business and customers.

Going Live

Ensure that each payment processing service is ready before going live with your store. Some businesses accept cash and card payments, while others only accept one or the other. Make sure everything is set up for a wide range of situations — in-person purchases or digital sales from an e-commerce website.

Once you’ve tested all aspects of your site and made any needed changes, you can set up automated billing for customers who want to make recurring purchases, like for monthly deliveries of a food subscription box.
It should be noted that payment gateway integration can be complicated and may necessitate technical knowledge. If you’re not comfortable with the technical elements of integration, you might want to hire a developer or work with a payment gateway provider that provides integration services.

Choosing a Payment Gateway Provider to Integrate

Payment gateways play a crucial role in the success of your business. So, it is important to do some research before settling for one. Here are some things to consider before choosing a provider:

Get Accustomed to The Pricing

Several financial institutions are involved in the payment process, making it complex. The payment gateway needs a fee to approve and complete transactions. All the different institutions that participate in the process require a fee. That is why this amount can become bulky. Usually, transactions are billed depending on the amount, type of product or service, and even location. 

The fees charged by each provider vary depending on their business model. Normally, you will get the following types of fees:

• Gateway setup fees
• Monthly gateway fee
• Merchant account setup
• Fee for every transaction processed

So it is crucial to thoroughly read and understand the pricing documentation provided by the payment gateway provider to avoid unwanted or hidden fees. 

Ensure Provider’s Transaction Limits Are Favorable

Fees and installation charges can’t be avoided. However, other financial aspects are critical when choosing a gateway provider. The transaction limit is one such option. Gateway providers often set a minimum and maximum amount for transactions. Merchants need to take note of both values depending on the types of products or services they provide. 

For example, it is not advisable to select Stripe with a minimum transaction value of $0.50, such as when your business sells products for less than that amount. It will greatly affect sales of those products and possibly your company’s success. 

Review Merchant Account Options

A merchant account is a record your business opens to handle transactions in the acquiring bank. Also, you are obligated to follow the credit card processing operational regulations set by credit card companies. 

You can open these accounts using payment gateway providers or banks that offer this service. So, the best course of action is to choose a payment gateway provider that offers a merchant if you already have one. 

Ensure the Gateway Supports Payment Methods Necessary For Your Target Market Location

You want to choose a payment gateway provider that supports as many payment methods as possible. As we have seen above, mobile wallets have become the favorite payment method, followed by credit/debit cards. Furthermore, ensure that a payment gateway provider supports all the required credit card networks. You don’t want customers complaining that their payments are being rejected. 

Another crucial aspect is multi-currency support. If your business operates globally, you should expect people to use their local currencies for purchases. So, the payment gateway provider should support these options with or without any additional fees.

While working on the Property Rental Marketplace project, one of the main tasks was to optimize a complex payment system with a multi-currency flow. We connected the platform to Stripe and fixed the existing Stripe code to exclude miscalculations in payment.

Automatic currency conversion was created with the help of a library working with the Central Bank. This provided the most comfortable conditions for users.

Users can cancel three bookings for free, and the fourth try will cost 15% of the total rental cost. The closer the check-in time is, the more the deduction will be charged when canceling.

Our team has also created a prepayment function. This made it possible to pay 50% of the rental price 90 days before the start of the lease.

Consider Mobile Payments

Mobile payments get the funds from credit/debit card accounts. However, they are still considered another form of payment. Apple Pay and Google Pay are the most popular ones. They have their own tokenization process. 

The tokenization replaces sensitive client data. For example, a BAN is replaced with a meaningless substitute known as a token.

These services are not available in all countries. However, the major ones support all four main credit card networks. So, check the provider’s documentation to ensure that they support mobile wallets. 

Make Sure Your Product Type is Not Prohibited by The Payment Vendor

Most providers generally accept or consider two types of products – physical and digital. However, there are some rare exceptions, where the provider may work only with one type. In that case, merchants selling physical and digital products should avoid such providers. 

Most Popular Payment Gateway Providers

Nowadays, with the popularity of payment gateways increasing, hundreds are scattered all over the market. However, let’s check out the top, most reliable options:

Paypal

PayPal Homepage

Customers will feel at ease choosing PayPal as a payment option on any site. This is because it is well-known and has been around for a while. The service is simple to set up, making it desirable for businesses, especially those just starting out. If business owners hesitate to use new payment methods, PayPal offers some comforting stats. According to PayPal, companies that utilize their service have an increase in checkout conversion rate by 44%. 

PayPal is a good alternative if you have a worldwide customer base since it accepts credit/debit cards worldwide. With support from 200 countries and 25 different currencies, you can be confident that your customers will be well-served where ever they are located. 

The pricing model for PayPal is complex and needs different calculations for international transactions, micropayments, and platform usage. 

Depending on your account’s volume and type, the fees may range from $1.90 to $3.49, with an additional $0.49 transaction fee for domestic transactions. For international commercial transactions, it is 1.50% of the total amount.

Amazon Pay

Amazon Pay Homepage

It has a reputation for quick and simple payments owing to the Amazon online marketplace. Many clients will be familiar with Amazon’s checkout process. They enjoy the convenience of one-click checkout. Millions of individuals already have an Amazon. Their ability to reuse financial processing data already saved in the users’ accounts means that the customer can expect a straightforward and simplified payment procedure. 

Amazon Pay is a wonderful option for merchants who want to customize their payment gateway. It interacts with your website’s API enabling you to customize the payment step with your own logo. The Amazon Pay fees are transaction-based and have an authorization and processing component. Domestic transaction fees are set at 2.9% + $0.30 for each transaction, and international transactions are set at 3.9%. There are no monthly or setup fees.

Stripe

Stripe Homepage

This is a payment gateway that allows for extensive customization. It is ideal for businesses that want complete control over their website. With the website’s API, it is simple to integrate the service. ECommerce business owners may also combine it with their current ERP, invoicing, and shopping cart systems. 

Stripe supports payments in 150 currencies. This makes it an excellent choice for those who have a worldwide audience. It also has a Bitcoin plugin that lets customers pay in Bitcoin. However, the costs for non-EU cards are greater. 

Stripe is also PCI compliant, making it an all-around good choice. Its downside is that it is not very suitable for inexperienced users. 

Stripe charges 2.9% for the integrated package with an additional $0.30 per transaction. They have no setup fees. Also, Stripe offers a customized package for large businesses. 

We have over six years of experience working with Stripe. A good example is The Skills project. This educational platform produces and distributes online lessons from the world’s top athletes like Michael Phelps, Maria Sharapova, and Shaun White. It also collects payments from end-users for subscriptions. 

For this type of platform, we optimized and integrated Stripe:

When we first started working with the client, they were already using Stripe. The Sloboda Studio team extended the Stripe payment feature on the Skills website. This made it possible to do payment transactions from different countries.

We also implemented various payment mechanisms that enable the Skills to:

• create the logic for the gift coupons and promo codes usage
• generate discount computing system
• optimize the payment flow using a link that activates the discount only for new users

There was a difficulty with the query-display effect because some vital information (discounts, promo codes, etc.) was stored in Stripe. If the discount needed to be deleted, there was no instant integration with the system, but a request for a Stripe came. We optimized this system to get an instant response.

We also helped integrate Stripe’s custom account with the Foody platform to allow users to make payments. Users can’t interact with Stripe directly; they interact only with the Foody platform.

Our team has enabled Stripe Link Integration. It automatically allows users to fill in the Stripe form if the user entered incorrect or incomplete information. This action reduces the number of rejected Stripe accounts that did not pass Stripe validation.

The payment function is currently valid only for the USA. However, our client plans to expand the platform’s coverage for countries where the Stripe system is also supported.

Shopify (Shopify Pay Installments)

Shopify Homepage

Shop Pay provides users with the option to pay for their goods in full at checkout or in installments for orders from $50 to $17,500. Customers can choose between the following installment payment options at checkout:

Four, twice weekly, interest-free payments for orders from $50 to $999.99.

Monthly payments from $150 to $17,500. Monthly installment payments come with interests from 10 to 36% APR.

Mobile Payments

Mobile payment is a way clients use to carry out transactions from your eCommerce platform using smartphones, tablets, and even smartwatches. 

As it is often said, “necessity is the mother of invention.” Ever since the invention of the mobile phone, people have tried to go full mobile – from programming complex apps on the phone to performing financial transactions. And today, it has become one of the most popular payment methods worldwide.  

Types of Mobile Payments and How They Work

There are four main types of mobile payments:

NFC

Near Field Communication (NFC) Mobile Payments are the way NFC-enabled point-of-sale and mobile device systems work together to process transactions. The encrypted information is passed from one device to another to complete payment. Apple Pay, Samsung Pay, and Google Pay are all mobile payments compatible with NFC technology.

Browser-Based Mobile Payments

Lots of smartphone browsers now have the ability to store card information and present it during checkout. It is a faster method on an eCommerce website. This is because customers don’t have to spend much time inputting card information. The payments are made through Card-Not-Present, which is added to the eCommerce mobile checkout page. 

In-App Mobile Payments 

These are similar to mobile browser payments. However, the card information is stored in the app. Also, users enter their financial information once, and it’s saved for future use. A lot of eCommerce apps have this feature, such as Amazon and eBay. Our company, Sloboda Studio, also implemented the same logic with in-app mobile payments for Split, the first marketplace for scooter rides in Los Angeles.

How We Integrated Different Payment Gateways in Our Projects

We’ve integrated several payment gateways into our projects. Here are some of them:

Veeqo

Veeqo Homepage

This is an omnichannel retail platform for various merchants. It allows you to manage your orders from multiple channels and keep track of inventory from multiple warehouses. 

Our main goal was to develop user profiles in the retailers’ system, create orders, and generate invoices.

Challenges

One of this project’s main challenges was to decrease the time required for payment handling. Veeqo used to handle them manually. All the invoices used to be arranged via bank transfers or phone. This manual system required a lot of time and resources.

Our Solution

To solve this issue, we decided to integrate Stripe. It enables acceptance of different types of payments. Also, it is convenient for both the Veeqo team and Veeqo customers.

Our team has enabled Stripe Account Link Integration. It automatically allows users to fill in the Stripe form if they enter incorrect information. This action helps to reduce the number of rejected Stripe accounts that did not pass Stripe validation.

Results

Started integration of React (as a front-end solution) and Stripe. We also connected AWS Lambda to unload Veeqo’s servers. Used Agile Scrum, one-call engineers, and our own expertise and initiative for effective communication. 

This platform was acquired by Amazon and raised over $4 million in March 2019.

Salita

Salita Homepage

This is a B2G (business to government) and B2C marketplace that offers access to different interpreters over video and phone conferences on a number of platforms (web, Skype for Business, apps).  

The initial goal was to build a Minimum Viable Product (MVP) to showcase the most important features to the first users and investors. 

Challenge

We needed to build a multi-currency flow function so that users from different countries, where there is a two-currency system, could pay and make a refund on the platform. 

Our solution

For well-regulated automatic multi-currency flow and exchange, it was important to adjust the central bank’s rate. Our team used Exchangerates.api library to convert currencies and transfer to the platform credit notes or make a money withdrawal.

Here’s how we added the gateway integration – Stripe:

• We had to optimize a complex system that supports a multi-currency flow. To do this, our team connected the solution to a Stripe account and fixed the existing Stripe code. 
• We also included automatic currency conversion using a library working with the Central Bank to create comfortable financial exchange conditions for users.

Results

Salita has raised more than $1.5M in two rounds of seed investments. The first was in February 2018 – NOK2,9M and the second in May 2019 in the amount of NOK5M.

Safhyre

This is an online platform for recruiting which connects employers with employees. SAFHYRE gives employers access to the database of job candidates.

The client’s main goal was to build an online recruiting platform from scratch. 

Challenges

One of the main challenges during the development of this project was integrating a payment gateway system. This is because most of the providers don’t work in the United Arab Emirates. So, we had to find a system that was supported in the UAE.

Solution

After much research, we came across PayFort. It is a friendly payment system that is used in the UAE. However, many restrictions on the banking system are imposed by the OAE state. That is why building a subscription system demanded numerous PayFort approves. 

Plus, Payfort has some API peculiarities, like a lack of proper documentation, requests had to be processed both on the front-end and back-end, and the URL feedback led to different places. We had to calculate the signature of the request manually. Also, there were typing errors in the Payfort API.

Results

Our team digitalized the offline business by building a web application from scratch. Sloboda Studio provided SAFHYRE with a full development cycle, namely back-end and front-end development, design, and QA. 

Custom Non-Hosted Payment Gateway: Is it Worth Creating From Scratch?

Building a payment gateway from scratch has its advantages and disadvantages.

Advantages Of Building From Scratch

No Payment Gateway Fees. When you get an off-the-shelf payment gateway like PayPal or Stripe, it often comes with sign-up costs and fees associated with each transaction. All of these extra fees can take a huge toll on your budget. Having your custom-built payment gateway will help avoid all these additional costs. 

Custom Features. Even off-the-shelf payment gateways with minimal fees often have many restrictions. For example, a third-party payment gateway may not support recurring payments or multiple-currency transactions. This will significantly limit your ability to do business. However, building a payment gateway tailored to your business needs will go a long way. Also, you can add and remove features freely. 

Offer Payment Gateway Products. Since you have full ownership rights to the custom-built payment gateway, selling it as a product to other businesses and agents is possible. It will bring in additional revenue to your business. 

Disadvantages of Building From Scratch

Despite all the advantages, there are also some downsides to creating it from scratch. One of the biggest concerns is development and maintenance costs. Development costs may be a one-time commitment. However, not all small and mid-sized businesses and startups have that amount of funds to spare. 

Building a payment gateway from scratch makes sense for big corporations like Amazon and Shopify. This happens when the number of fees becomes so negative that it’s cheaper to build a payment gateway from scratch. Another downside is the lengthy certification needed to integrate with payment processors. 

The hands-on cost and challenges in obtaining certification make building a payment gateway from scratch less favorable. To compete with other transaction platforms like PayPal and Stripe for market space, then it is worth building from scratch. If not, using one or more payment gateway providers is the best option. 

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How to Get Payment Gateway Compliant With Industry Requirements

Your business must comply with industry standards to process and store sensitive financial data. It must comply with Payment Card Industry Data Security Standard (PCI DSS) to accept card payments. Here are some steps to become compliant:

• Set your compliance level. Compliance comes in four levels determined by the number of safe and successful transactions your company has completed. The transactions don’t count if it is not done through Visa, MasterCard, Discover Card, or American Express. 
• Get acquainted with the PCI Self-Assessment Questionnaire (SAQ). This is the set of requirements needed for compliance. 
• Complete the Attestation of Compliance (AOC). After studying the SAQ, you need to take the AOC exam. There are nine types of AOC for businesses. 
• Conduct an audit by the Approved Scanning Vendor (ASV). 
• Submit your documents to the card associations and acquire them. Once all is done, you need to submit the SAQ and AOC, together with the ASV scan report. 

In a Nutshell

Payment gateways are a vital part of the digital eCommerce ecosystem. They reduce some barriers to eCommerce by providing a safe and secure transaction method for customers to pay for goods and services online. 

The benefits of payment gateways can’t be contested. However, the decision to get an off-shelf or custom-built payment gateway system for any transaction will depend on the specific needs of your business. Sloboda Studio has been in the app development market for over 13 years. And we are experts in building solutions from scratch. We have built many different solutions, like Veeqo and Salita, that require payment gateway integrations. Contact us if you want to build a platform that requires payment gateway integration.