The 8 Best Payment APIs For Small Business Transactions

Total Rating	4.9
Fees & Rates5.0
Products & Services4.4
Contract5.0
Sales & Advertising Transparency5.0
Customer Service4.8
User Reviews4.5

Pros

Transparent interchange-plus pricing
No long-term contracts
Good developer resources

Cons

Not suitable for high-risk industries
May not be cost-effective for very low volume businesses

Why Helcim Is The Payment API For Growing Businesses

Helcim is one of our favorite payment processors, and it's not too hard to see why. Helcim offers transparent interchange-plus processing, no long-term contracts, and extensive fee disclosures. Not only that, but it also scales well with business growth and can handle international payments.

Compared to some of the other services on this list, Helcim's developer tools fall somewhere in the middle of the pack. They're more than serviceable, however, with a folder-like layout and ample screenshots. The Helcim API is a RESTful API and can be used with any language that can make an API call. In an interesting desktop layout choice, code samples live just offscreen and can be slid on or off the center of your screen with a click.

Helcim Payment API Features

While it may not be as well-known a name as Square or Stripe, Helcim is an all-around excellent payment processor with an API that covers most of the bases.

Credit & debit cards
ACH
Google Pay
Apple Pay
Invoices
Inventory management
Support for Canadian payment methods
Customer management
Card vault

Helcim Pricing

Interchange + 0.40% + $0.08/card-present transaction (volume discounts available)
Interchange + 0.50% + $0.25/card-not-present transaction (volume discounts available)
Helcim Card Reader — $109/unit
No monthly or annual account fees
No PCI compliance fees
No monthly minimum

Ideal For...

Business that may grow quickly

Get Started With Helcim

Stax: Best For eCommerce Businesses

Stax

Total Rating	4.2
Fees & Rates4.1
Products & Services5.0
Contract4.6
Sales & Advertising Transparency3.5
Customer Service4.0
User Reviews3.8

Exclusive Promo: Get your first month free with Stax. Learn More

Pros

Good for high-volume sellers
Impressive feature set
Upfront pricing and fees

Cons

Expensive for low-volume sellers
Not available for high-risk businesses

Why Stax Is The Best Payment API For eCommerce Businesses

Stax is best suited for larger businesses with a high number of sales, and it also caters its services to businesses that do the bulk of their selling online. Stax has a wide variety of integrations with shopping carts. It also has its own website builder.

Stax is also an excellent choice for businesses that sell software or online services like subscriptions. Stax has upfront pricing that takes the guesswork out of processing fees but its rates may be a bit high for smaller volume sellers. Its strong feature set also makes Stax a very viable option for in-person sellers as well.

Stax Features

Stax has an extensive feature list with everything you would expect from a payment processor, including:

Integrated payment processing platform
Built-in shopping cart
Virtual terminal
Recurring invoices
QR code and text payments
Mobile processing capabilities
ACH processing
Quickbooks integration

Stax Pricing

$99-$199/month depending on sales volume
$0.08-$0.15 + interchange

Ideal For...

Businesses that primarily sell online

Get Started With Stax

Stripe Payments: Best For Developer Resources

Stripe Payments

Get Started With Stripe Payments

Total Rating	4.7
Fees & Rates4.7
Products & Services4.5
Contract5.0
Sales & Advertising Transparency5.0
Customer Service4.5
User Reviews4.1

Pros

Predictable flat-rate pricing
Excellent developer resources
Excellent support for international currencies & payment methods

Cons

Account stability issues
Not suitable for high-risk industries

Why Stripe Is The Best Choice For Businesses That Want Access To Excellent Developer Resources

When it comes to developer support--always important where payment gateways are concerned--Stripe is pretty close to the gold standard for payment processors. The online documentation is exhaustive, easy to parse, and full of readily accessible code snippets in each of the server-side languages it supports (Ruby, Python, Java, PHP, Node.js, Go, and .NET). Stripe also has links to boilerplate projects you can clone and build upon.

Stripe Features

How does Stripe work? Well, Stripe combines the functionality of a third-party payment processor and a gateway into a single package. This will be convenient for many businesses, provided they don’t already have a merchant account that they want to hold onto, as Stripe doesn’t let you use its gateway à la carte; it’s all or nothing. Stripe’s API is deep and versatile, especially when it comes to eCommerce. Features include:

Credit & debit cards
ACH
Google Pay
Apple Pay
Invoices
International currency support
International payment method support
Account routing by currency

Stripe Pricing

No monthly fees for a basic account
2.9% + $0.30/online credit/debit transaction (+0.5% for manually entered transactions)
2.7% + $0.05/in-person credit/debit transaction via Stripe Terminal
+1.5% for international cards
+1% for currency conversion (if required)
0.8%/ACH direct debit transaction ($5.00 maximum)
1.2%/ACH direct debit transaction (two-day settlement)
$1.00/ACH credit payment
$1.50/instant bank account validation
Additional fees for optional add-on services

Please refer to our full breakdown of Stripe’s pricing for additional details.

Ideal For...

Businesses with skilled developers

Square: Best For New & Seasonal Businesses

Square

Total Rating	4.8
Fees & Rates5.0
Products & Services4.7
Contract4.3
Sales & Advertising Transparency5.0
Customer Service4.9
User Reviews4.9

Get a free card swiper from Square at no cost when you create a free account. Claim your card reader.

Pros

Predictable flat-rate pricing
Enables omnichannel selling
Excellent public documentation

Cons

Account stability issues
Not suitable for most high-risk industries

Why Square Is The Best Payment API For New & Seasonal Businesses

Square is more or less synonymous with "quantity of features." You'll get a lot of functionality out of this processor, and all without paying a monthly fee.

As you may expect of an ecosystem as large and complex as Square's, several different Square APIs allow developers to access different parts of the processor's infrastructure. Thankfully, Square provides an API Explorer to help you find what you need. Square provides ample documentation on its developer site, custom SDKs, and a sandbox to make development easier.

Square Features

Square’s payment gateway allows users to access aspects of its “full-stack” payment service. Square has built up an enormous platform that provides a variety of tools to both eCommerce and brick-and-mortar businesses — including marketing, loans, loyalty programs, productivity, inventory, etc. — on top of processing card transactions. API features include support for:

Credit & debit cards
ACH
Google Pay
Apple Pay
Payouts
Invoices
Inventory control
Customer management
Loyalty programs
Booking
Team management
Proprietary gateway

Square Pricing

No setup or application fees
$0/month for Square Free account ($29+/month for Square Plus accounts)
2.6% + $0.10/card-present transaction
2.9% + $0.30/online transaction
3.5% + $0.15/manually keyed-in transaction
2.9% + $0.30/invoice paid via credit or debit card
3.5% + $0.15/invoice paid via card on file
1%/ACH transaction (minimum $1 charge)
No ACH reject or chargeback fees
Square Contactless & Chip Reader — $49 each
Square Stand With Contactless & Chip Reader — $169
Square Terminal — $299
Square Register — $799 (or $39/month for 24 months)

For a deep look at costs associated with Square, check out our guide to Square pricing.

Ideal For...

Businesses just starting out

Get Started With Square

Host Merchant Services: Best For Customer Service

Host Merchant Services

Get Started With Host Merchant Services

Total Rating	4.9
Fees & Rates5.0
Products & Services5.0
Contract5.0
Sales & Advertising Transparency4.7
Customer Service4.6
User Reviews4.8

Pros

Transparent interchange-plus pricing
No long-term contracts
No monthly minimums

Cons

Can be expensive for low volume merchants
Monthly fees can add up

Why Host Merchant Services Is The Best Choice For Businesses Looking For Strong Customer Service

Host Merchant Services gets high marks for its customer service, which also extends to its developer support and easy-to-use API. Popular gateways like Authorize.Net are easily added to the service. Additionally, Host Merchant Services offers interchange-plus pricing to all of its clients, with guaranteed rates for the life of the account, making it a reliable, cost-effective processor for mature businesses.

HMS does not charge any early termination fees or have long-term contracts. In fact, HMS will even pay up to $250 in early termination fees for referred clients ($500 in the client processes over $50,000/month) if they leave their current processor for HMS.

Host Merchant Services Features

Host Merchant Services runs a bit leaner than the big third-party processing platforms but still provides a lot of value for the price. Features include:

Credit & debit cards
ACH
Google Pay
Apple Pay
Shopping cart integration
Web hosting
Featured payment gateways:
- Transaction Express
- Authorize.Net
- NMI Gateway

Host Merchant Services Pricing

No application or setup fees
$14.99/month account fee
Interchange + 0.25% + $0.10/retail transaction
Interchange + 0.20% + $0.09/restaurant transaction
Interchange + 0.35 + $0.10/eCommerce transaction
$5.00/month gateway fee (optional)
$15 chargeback fee
No PCI compliance fee
No early termination fee

Ideal For...

Businesses needing extensive support

Authorize.Net: Best Portable Payment Gateway

Authorize.Net

Get Started With Authorize.Net

Total Rating	4.6
Fees & Rates4.7
Products & Services5.0
Contract4.8
Sales & Advertising Transparency4.6
Customer Service4.7
User Reviews2.0

Pros

Versatile standalone payment gateway
Live console available in documentation
Excellent developer resources

Cons

Expensive if not included in bundle
Requires a payment processor as well

Why Authorize.Net Is The Best Portable Payment Gateway

As a dedicated payment gateway, Authorize.Net can connect your online store to your payment processor, provide support for multiple currencies, add security features, provide recurring billing services, and enable echeck processing.

In terms of developer resources, Authorize.Net may be one of Stripe's closest rivals. There's a ton of documentation, including API references, developer guides, and a collection of PCI-compliant tools called the Accept Suite. Most of it is publicly viewable, so you can check it out before you commit to anything. Much of the documentation contains an API live console, so you can test out snippets of code without leaving the resources.

Most importantly, Authorize.Net can be paired with a huge number of merchant services.

Authorize.Net Features

Most of the other services on this list have been payment processors. Authorize.Net, however, is a standalone payment gateway offered by Visa. You’ll often see it bundled with other services (which is how we’d recommend you use it). Remember, you’ll still need a merchant account/payment processor to process credit cards with Authorize.Net.

Credit & debit cards
ACH
Google Pay
Apple Pay
Customer information management
Syncs with Quickbooks
Advanced fraud detection
International currency support

Authorize.Net Pricing

Note, Authorize.Net pricing varies depending on the services it’s bundled with. Below is the default cost of adding Authorize.Net to an existing merchant account. If you get Authorize.Net through a bundle offered by your merchant account provider, the fees will generally be lower.

Monthly fee: $25
Transaction fee: $0.10

Ideal For...

Businesses seeking processing flexibility

Braintree Payment Solutions: Best For PayPal Integration

Braintree Payment Solutions

Get Started With Braintree Payment Solutions

Total Rating	4.5
Fees & Rates4.4
Products & Services5.0
Contract5.0
Sales & Advertising Transparency4.8
Customer Service3.8
User Reviews3.1

Pros

Predictable flat-rate pricing
Excellent developer resources
Integrates with PayPal ecosystem
Full merchant account with payment platform perks

Cons

Not suitable for high-risk industries
Transactions rates are expensive relative to competitors
Standalone gateway option is costly

Why Braintree Is The Best For PayPal Integrations

At first glance, Braintree's profile is very similar to Stripe's -- they both combine payment services and gateway functionality with an eye toward international eCommerce.

There are two important differences at this level, however. The first is that Braintree provides a merchant account rather than third-party processing, so you're getting better account stability, but you should expect to have to jump through some additional hoops and wait times to set it up. And unlike Stripe, it is possible just to use Braintree as a payment gateway if you already have a merchant account. I wouldn't recommend this, though, as using Braintree's gateway à la carte is more expensive than most other independent gateways.

For developers, Braintree provides sandbox accounts to explore the service's functionality. The online documentation is extensive if not quite as slickly presented as Stripe's -- you have to toggle between programming languages at the top of each page rather than each code snippet, for example. The payment API reference section for developers is well laid out, however, making it easy to look up the methods you'll need when you need them.

Braintree Features

Braintree is part of the PayPal payment services family, along with sister services PayPal (PayPal review) and Venmo (Venmo review). It does, however, function semi-autonomously from the other companies and has a slightly different focus.

Credit and debit card processing
ACH
PayPal
Venmo
Apple Pay
Google Pay
Samsung Pay
Currency conversion
Gateway can be used standalone
Support for international payment methods
Excellent developer tools
Access to PayPal ecosystem

Braintree Pricing

Braintree is funded through transaction fees, so there are no recurring fees for the basic service. If you use the gateway as a standalone, which we don’t recommend, these are the monthly fees:

Gateway fee:$49/month
Gateway transaction fee: $0.10
Additional merchant accounts (beyond the first): $10/month

If, on the other hand, you Braintree as your payment processor, these are the costs:

No monthly fee
Credit & debit cards:2.59% + $0.49
ACH:0.75% (max. $5)
Venmo: 3.49% + $0.49

Ideal For...

Businesses already selling with PayPal

GoCardless: Best For Standalone ACH processing

GoCardless

Get Started With GoCardless

Pros

Cost-effective ACH solution
International bank-to-bank transfers
Low transaction fees

Cons

No credit/debit card processing support
API access locked behind monthly fee

Why GoCardless Is The Best Payment API For Standalone ACH Processing

The ability to process ACH payments provides merchants with a strong alternative to credit card payments, especially where recurring and subscription payments are concerned. While some payment processing platforms include ACH out of the box, it's a bit more uncommon to find affordable standalone ACH services. Businesses looking for such a service should consider GoCardless, a simple and cost-effective way to get ACH payments with no added bloat.

As a bonus, you'll also get international payment service through Wise.

GoCardless Features

GoCardless’s features are oriented around ACH payment customization and security.

ACH
International transfers (Wise)
Subscription/recurring payments
Online customer sign-up
Bank verification
Reporting tools
Branded payments(Plus and Pro)
Payment page customization (Plus and Pro)
API access (Pro)

GoCardless Pricing

Pay-as-you-go: No monthly fee
Plus package:$25/month
Pro package:$75/month
ACH transaction fee:1% + $0.25 (max $2.50)
- Additional fee for transactions over $1,000: 0.3%
International transaction fee: 2% + $0.25 (includes currency conversion)

GoCardless’s plans do not have any long-term contracts or early termination fees.

Ideal For...

International sellers

Payment Processing Rating Methodology

Merchant Maverick has been researching the payment processing industry since 2009. Our writers have reviewed hundreds of credit card processors, merchant account services, and mobile payment apps, evaluating each provider carefully on several different metrics.

Weighted Rating Breakdown

Fees & Rates 35%

Contract 20%

Products & Services 15%

Sales & Advertising Transparency 15%

Customer Service 10%

User Reviews 5%

When comparing different payment processing companies and applications to one another, we consider numerous data points. Our experts start by comparing credit card processing rates, the presence of additional fees, contract length, sales practices, and the presence or absence of additional features and services, like point of sale software. Each provider is judged on its own merits and how well it stacks up to industry standards; then it is weighed against the other providers on the list.

We spend an average of 10-15 hours researching and updating each one of our lists, making sure every company or application included meets our internal standards for quality and reputation. Any list of recommended payment processors on our site might contain a mix of standard merchant accounts, third-party payment processors, mobile payment devices, and high-risk payment processors, depending on what our expert feels is the best fit for certain scenarios or business types.

For additional details about Merchant Maverick’s review and rating processes, please refer to any or all of the following methodology pages:

Years reviewing payment processors

100+

Providers evaluated

Attributes and features assessed per vendor

40+

Years combined experience

What To Look For In A Payment Processor API

What makes a good payment processor API? There are a few factors I’d keep in mind when you’re looking for a developer-friendly payment processor.

Support For Multiple Payment Methods

While this may not be the case for every business, one of the most common reasons to use an online payment API is to expand and customize the payment methods you can offer your customers. If you’re looking to accept more than major credit or debit cards, want to take international payment methods, or experiment with alternatives like cryptocurrency, you’ll probably want a good payment API.

Customizability

All payment APIs offer some customization options, but does it just allow you to tinker around the edges, or does it offer enough depth to enable you to build what you want to build? Check any publicly available documentation to get a sense of what the API can do before you signup.

Is The API Behind A Paywall?

Pricing is still the name of the game, no matter how much hacking you plan on doing. Make sure the provider’s pricing scheme works with your transaction volume and, preferably, allows for month-to-month contracts.

Additionally, there’s no excuse for hiding developer resources behind a paywall in this day and age, especially when some of the bigger and more innovative payment processors offer it by default.

Security

Most of the services above use some form of tokenization, so credit card information never ends up residing on your machine. Depending on the company, your PCI responsibilities may vary, so make sure you read through their documentation to find out what they take care of and what they don’t.

Quality Of Documentation & SDKs

Many payment service providers offer payment APIs, but many of them hide them from the public. As a rule, I think it’s a good idea to be able to skim their documentation and get a sense of whether it’s a tool you want to work with.

Your mileage may vary here depending on your preferences, but some developers may appreciate having custom libraries and other labor-saving perks available to them.

Does It Have An Active Developer Community?

Poke around the forums and see how active a developer community the product has. The more active it is, the more likely you’ll be able to have questions answered quickly and be able to make use of existing integrations and code.

Payment Processing Costs & Payment APIs

While some APIs are free to use, that’s not the case when it comes to payment processors. If you’re using a payment API, that usually means you’re going to have to be a customer of that payment processor.

That said, costs will vary greatly depending on the payment processor. Some processors, such as Stripe, will give you access to their API as part of the basic service. Since it’s a month-to-month service with no monthly fee, you’ll only pay the transaction costs, plus any premium features you sign up for. With other payment processors, the API may only be available if you are buying a premium plan.

Costs for payment API usage may include:

Transaction Fees: This is the amount of money that will be deducted from each of your sales. This amount will vary by payment method. While it’s usually the same regardless of whether you’re using an API or not, some APIs may allow you to use surcharging to pass on some costs to your customers.
Monthly Fees: These are membership fees you pay to keep your account going. Not all processors charge monthly fees. Some will only charge monthly fees for premium plans.
Gateway Fees: APIs are frequent functions of payment gateways. Some payment processors have integrated payment gateway APIs, while others use third-party gateways. Be aware of any additional monthly or transaction fees you have to pay to use a payment gateway.

How To Choose The Best Payment Gateway API For Your Needs

Now that we’ve covered some of the heavier hitters in the payment processing API department, you should be able to dig in a little further and match their capabilities to your needs. Even the best credit card processing companies may not offer the API access you’re looking for.

Take stock of your developers’ strengths and encourage them to poke around publicly available documentation; they can give you a good idea of whether the platform can be hammered into the small business credit card processing tool you need.

If you’re going to be tinkering with a payment API, it might be a good time to brush up on PCI compliance and security features, such as credit card tokenization and fraud detection. If you’re looking to customize your payment workflow, you may also want to read up on everything you need to know about alternative payment methods.

Bio
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Chris Motola

Expert Contributor at Merchant Maverick

Chris has been writing about small business topics since 2003. He has been featured in Fox Business, ABC News, Yahoo Finance, GoBankingRates, Newsweek, BizJournals, and other publications. He has a Bachelor’s of Arts in English Writing Arts from SUNY Oswego, and a Masters of Science in Interactive Media from the University of Central Florida. He currently resides in the Hudson Valley region of New York.

View Chris Motola's professional experience on LinkedIn.

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1. Helcim

❮ ❯

Easy scaling for growing businesses
Monthly fees: $0+
Interchange-plus pricing

2. Stax

❮ ❯

Excellent for online sellers
$99-$199/month
Interchange + $0.08-$0.15 per transaction

3. Stripe Payments

❮ ❯

Best for developer resources
No monthly fee
Flat-rate pricing

4. Square

❮ ❯

Best for new & seasonal businesses
Monthly fee: $0+
Flat-rate pricing

5. Host Merchant Services

❮ ❯

Excellent customer service
Monthly fee: $14.99
Interchange-plus pricing

6. Authorize.Net

❮ ❯

Portable gateway that can be used with many different processors
Monthly fee: $25 (varies by bundle)
Pricing model varies by merchant services used

7. Braintree Payment Solutions

❮ ❯

Access to PayPal ecosystem with full merchant account
No monthly fee (standalone gateway is $25/month)
Flat-rate pricing

8. GoCardless

❮ ❯

Standalone bank-to-bank transfers
Monthly fee: $0+
Flat-rate ACH processing