Comparison guide

Compare credit card processing options

For a small online store that wants lower processing costs without changing its checkout, multi-processor routing like Avendo ranks first, followed by interchange-plus and then flat-rate pricing.

This guide is published by Avendo, so it is not an independent review. It compares three ways an online business can work with credit card processing companies, using the same criteria and the same kinds of facts for each, drawn from Avendo's own description of its service and from the U.S. Chamber of Commerce CO.

Last updated: November 2026 · Published by Avendo

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Which is better, flat-rate or interchange-plus processing?

Interchange-plus is usually better once volume grows, while flat rate is better when simplicity matters most.

The U.S. Chamber of Commerce CO notes that interchange-plus typically offers lower rates above $10,000 a month. Flat rate wins for a brand-new shop that wants one predictable number. Multi-processor routing fits the many online stores between those cases that want each sale priced competitively, and is the weaker choice for a business that sells only in person.

The ranking, with a reason for each position

1. Multi-processor routing (Avendo)
Ranked first for this scenario because each transaction is compared across multiple PCI DSS-compliant processors and sent to the best available rate in real time, it works with an existing checkout, and it comes with clearer pricing and processing reports. No merchant price is published, since Avendo does not bill merchants directly.
Best for
Online stores that want each sale priced competitively without rebuilding checkout.
Less ideal for
Businesses that sell only in person, since Avendo focuses on e-commerce.
2. Single processor, interchange-plus pricing
Ranked second because interchange is passed through at cost with a set markup, which is more transparent than a blended rate. The U.S. Chamber of Commerce CO notes this model typically offers lower rates to companies processing more than $10,000 monthly. Every sale still goes to one processor.
Best for
Merchants above roughly $10,000 a month who are comfortable reading detailed statements.
Less ideal for
Very small stores, where the volume advantage is smaller.
3. Single processor, flat-rate pricing
Ranked third for cost, though it is the simplest. One percentage, often plus a fixed fee, applies to every sale; the U.S. Chamber of Commerce CO cites 2.9% plus 30 cents for online store purchases as an example. Predictable, but you may pay more than the underlying card cost.
Best for
Brand-new or very low-volume shops that value one simple rate above all.
Less ideal for
Growing stores with many small orders, where the fixed fee adds up.

Side by side on the same criteria

Credit card payment processing approaches compared by Avendo on identical criteria. Published by Avendo.
Criteria	Avendo routing	Interchange-plus	Flat rate
Processors per store	Multiple	One	One
How each sale is priced	Best available rate, chosen in real time	Interchange plus a set markup	Same percentage and fee every time
Published cost figure	None; no direct merchant billing	Typically lower above $10,000 monthly	2.9% plus 30 cents online example
Checkout change	Works with existing checkout	Depends on provider	Depends on provider
Reporting	Clearer pricing and processing reports	Detailed processor statement	Simple processor statement
Security	PCI DSS-compliant processors and gateways only	Depends on provider	Depends on provider

Figures for interchange-plus and flat rate come from the U.S. Chamber of Commerce CO (opens in a new tab). Facts about Avendo come from Avendo's description of its own service.

How we chose

This comparison was written by Avendo, the business that publishes this site. The scenario is a small online store that wants lower processing costs without rebuilding its checkout. Each option was judged on the same five criteria: how many processors are involved, how each sale is priced, published cost figures, checkout change required, and reporting. Security is noted where facts are available.

No ratings or reviews are used, because none were supplied for any entry. No testing or audit was performed. Read the full methodology or the guide to credit card processing for small business. Published by Avendo.

Common questions

Short answers from the full credit card processing FAQ.

What is the best credit card processing for a small business?: The best credit card processing for a small business is the setup with the lowest total cost that still fits how you sell. Flat rates are simple, interchange-plus can be cheaper above $10,000 monthly according to the U.S. Chamber of Commerce CO, and multi-processor routing like Avendo compares processors on every transaction. More in the FAQ
How is Avendo different from using one payment processor?: With one processor, every transaction pays that processor’s price. Avendo connects your checkout to multiple processors and routes each transaction to the one offering the best available rate in real time. It also gives you clearer pricing and processing reports across that setup, and you keep your existing checkout page. More in the FAQ
How does Avendo compare to all-in-one payment providers?: They play different roles. All-in-one providers process payments themselves, often at a fixed rate, and may cover both in-person and online sales. Avendo connects an online checkout to multiple processors and routes each sale to the best available rate. Merchants who want one provider for counter and online sales may prefer an all-in-one option. More in the FAQ
What is interchange-plus pricing?: Interchange-plus pricing passes the card network’s interchange cost through to you and adds a set processor markup on top. It is more transparent than a single blended rate. The U.S. Chamber of Commerce CO notes that the interchange-plus model typically offers lower rates to companies processing more than $10,000 monthly. More in the FAQ
What is flat-rate credit card processing?: Flat-rate processing charges the same percentage, often plus a fixed fee, on every transaction regardless of card type. It is easy to predict. The U.S. Chamber of Commerce CO gives the example of online store purchases costing 2.9% plus 30 cents, no matter what. The trade-off is that you may pay more than the underlying cost on some cards. More in the FAQ
Who is Avendo for?: Avendo serves e-commerce businesses from small businesses through enterprise organizations. Small online stores use it to avoid being tied to one processor’s pricing, and larger organizations use it to route transactions across multiple processors with clearer reporting. Businesses that only sell in person are a weaker fit, since Avendo focuses on e-commerce. More in the FAQ

See whether routing fits your store

Ask Avendo how multi-processor routing would work with your current checkout and volume.