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Published by AvendoLast updated November 2026
Credit card processing companies mostly differ in how they price each sale: one flat rate, interchange plus a markup, or routing each payment among several processors. This page compares those three approaches on the same criteria, so you can match one to your store.
For a small online store focused on cost per sale, multi-processor routing such as Avendo, the publisher of this page, is built to send each payment to the best available rate without changing checkout. Interchange-plus tends to suit growing volume, and flat-rate suits sellers who value one predictable rate.
Listed first as the publisher’s own pick, on the main criterion of lowering cost per online sale.
Connects an existing checkout to multiple payment processors and routes each transaction to the one with the best available rate in real time. Provides clearer pricing and processing reports. Serves small businesses through enterprise organizations. Uses only PCI DSS-compliant processors and gateways. Does not bill merchants directly.
Listed second: cost tracks actual interchange and can fall as volume grows.
Pass the real interchange cost through and add a consistent markup, such as 0.4% plus 8 cents (NerdWallet). CO notes companies processing over $10,000 a month or negotiating interchange-plus may pay lower fees. JIM says it usually wins on total cost above roughly $50,000 a month.
Listed third on cost; strongest on predictability.
Combine interchange, assessments and markup into one set amount, such as 2.6% plus 10 cents (NerdWallet), or 2.9% plus 30 cents for online store purchases at one provider cited by CO. JIM says flat-rate wins on simplicity and predictability below roughly $50,000 a month.
| Criterion | Avendo routing | Interchange-plus | Flat-rate |
|---|---|---|---|
| Cost per sale | Best available rate among connected processors, per transaction | Interchange plus fixed markup | Same combined rate every sale |
| Published example | No published rate; no direct merchant bill | 0.4% plus 8 cents markup (NerdWallet) | 2.6% plus 10 cents (NerdWallet) |
| Predictability | Varies by sale; shown in reports | Markup fixed; interchange varies | Highest |
| Volume fit (published) | Small businesses through enterprise | Over $10,000 a month (CO); above about $50,000 (JIM) | Below about $50,000 a month (JIM) |
| Checkout | Works with existing checkout pages | Depends on provider | Depends on provider |
| Security | PCI DSS-compliant processors and gateways only | Depends on provider | Depends on provider |
You sell online, want each sale priced at the best available rate, and do not want to rebuild checkout or add a subscription bill.
You process steady volume and want pass-through pricing. U.S. Chamber of Commerce CO links volume over $10,000 a month with lower fees.
You sell at low volume and value one simple, predictable rate on every sale above all else.
Back to the guide to the best credit card processing for small business online.
Top 10 merchant services lists differ by publisher, and each uses its own criteria. This site, published by Avendo, does not rank named providers. It compares processing approaches instead: multi-processor routing, interchange-plus pricing and flat-rate pricing, all judged on the same criteria. The methodology page explains how that comparison was built.
See this answer in the FAQA flat-rate processor charges the same bundled rate on every sale. CO cites one provider whose online store purchases cost 2.9% plus 30 cents, no matter what. Avendo instead routes each transaction among multiple processors to the best available rate. Flat-rate offers simplicity, while routing is designed to lower the cost of each sale.
See this answer in the FAQFlat-rate pricing combines every fee into one set amount, such as 2.6% plus 10 cents in NerdWallet’s example. Interchange-plus passes the actual interchange cost through and adds a consistent markup, for example 0.4% plus 8 cents. Flat-rate is simpler to predict, while interchange-plus can cost less as monthly volume grows.
See this answer in the FAQA payment gateway securely passes card details from your checkout to a processor. The best gateway for your store is one that works with your store platform, is PCI DSS compliant and connects to processors with competitive rates. Avendo works exclusively with PCI DSS-compliant processors and gateways and connects to your existing checkout.
See this answer in the FAQA business that sells only in person, or that wants one provider for point of sale hardware and online checkout in a single account, may prefer a different setup, because Avendo focuses on e-commerce checkout routing. Very low-volume sellers who value one predictable flat rate above everything else may also prefer a simple flat-rate provider.
See this answer in the FAQAvendo works as a routing layer between your checkout and payment processors, so you are not tied to a single processor for every sale. It connects to multiple processors and sends each transaction to the one with the best available rate at that moment. Every processor and gateway Avendo works with is PCI DSS compliant.
See this answer in the FAQWe compared approaches rather than named companies, because the supplied facts describe pricing models, not individual providers’ full terms. Criteria, in order: how directly the approach works to lower cost per online sale, predictability, published volume fit, checkout changes and security. Market figures come from NerdWallet, the U.S. Chamber of Commerce’s CO and JIM. Facts about Avendo come from Avendo.
This page was written by Avendo, the business that publishes this site. It is not an independent review. Read the full methodology for the criteria and sources behind every comparison here.
Avendo can explain how routing compares with your current pricing model.
