Which payment processor has the lowest fees for online payments?

Assuming you’re in the U.S. and mean standard online card payments: PayPal’s Expanded Checkout has the lowest published flat rate among the options I checked: 2.89% + 29¢ per transaction. Stripe and Square’s online API rate are 2.9% + 30¢; PayPal’s own PayPal/Venmo checkout costs more. (paypal.com)

That’s not necessarily the cheapest for your business: rates can depend on transaction size, card mix, volume, and payment method. For higher sales volume, compare a processor with interchange-plus pricing, such as Helcim, against your actual processing statements; it may work out cheaper, but there isn’t one universal lowest-fee processor. (legal.helcim.com)

There isn't one processor with the lowest fees for everyone. The answer depends mostly on your monthly volume and whether you sell online only.

• Small sellers: Stripe is the common pick. For standard US online card payments, Stripe and Authorize.net both charge 2.9% + 30¢, but Authorize.net adds $25 per month. Square's online rate is sometimes listed the same, but one comparison puts its free-plan online rate at 3.3% + US$0.30, so check the current plan details.
• Mid-volume sellers: Helcim is often cited as cheaper because it uses interchange-plus pricing. One guide says it passes on the interchange rate the card networks charge and adds its own margin, which for keyed and online payments starts at 0.50% + US$0.25 on monthly volume under US$50,000. Its rates have to be confirmed directly with the provider.
• High-volume sellers (roughly $250K–$500K+ per month): Adyen can be cheapest. One source says above this threshold, Adyen's lower per-transaction costs outweigh the setup and platform fees. Its pricing is custom and it generally requires enterprise onboarding.
• Shopify stores: Shopify Payments can be the lowest total cost, since Shopify charges 0.5%–2% on top of other processors if you don't use its own payments.

PayPal is usually the most expensive for standard online checkout, at 3.49% + 49¢ for a standard US online card payment, though it may convert better because customers recognize it.

The sources disagree on some figures, and many are comparison sites that may earn referral fees. Before choosing, estimate your own cost using your average order size, monthly volume, and card mix, and check each provider's current pricing page.

There is no single "lowest fee" payment processor that works for everyone. The best option for your business depends heavily on your monthly transaction volume, average order value, and where you are located.

To find the lowest cost, you must look beyond the "headline" rate (often around 2.9% + $0.30) and understand the three common pricing models.

1. Understanding Pricing Models

• Flat-Rate Pricing (Best for Startups/Low Volume):
  • Examples: Stripe, Square, PayPal.
  • How it works: You pay a fixed percentage and fee for every transaction, regardless of the card type.
  • Pros: Highly predictable, easy to set up, no monthly fees.
  • Cons: Often the most expensive option as your business grows.
• Interchange-Plus Pricing (Best for Scaling/High Volume):
  • Examples: Helcim, Adyen, Payment Depot.
  • How it works: You pay the "interchange" fee (the actual cost set by card networks) plus a small, transparent markup from the processor.
  • Pros: Generally the lowest cost for businesses with consistent or high volume.
  • Cons: Fees can fluctuate; slightly more complex to understand.
• Subscription/Membership Pricing (Best for High Revenue):
  • Examples: Stax.
  • How it works: You pay a flat monthly subscription fee in exchange for paying near-wholesale processing rates.
  • Pros: Can result in significant savings if you process a large amount of money monthly.
  • Cons: The monthly cost is a fixed expense that must be justified by your volume.

2. Summary Comparison

3. Key Factors to Watch

• Total Cost of Ownership: Don’t just look at the percentage. Check for monthly account fees, setup fees, PCI compliance fees, and chargeback fees, which can quickly outweigh a slightly lower transaction rate.
• International Sales: If you sell globally, processors like Airwallex may offer lower costs for cross-border transactions by avoiding "forced" currency conversion markups.
• Hidden Savings: If your volume is low (e.g., under $10,000/year), the difference between processors is often negligible (a few dollars a year). In this case, ease of use and integration with your website are usually more important than the transaction rate.

Recommendation: If you are just starting out, Stripe or Square are industry standards for their ease of use and flat-rate predictability. If your business is scaling and you want to reduce your "effective rate," look into Helcim (interchange-plus) or Stax (subscription) to see if your monthly volume justifies the shift. Always request a custom quote from sales teams if you process significant monthly volume.

There isn’t one universally cheapest processor: fees depend on your country, card type, transaction size, and sales volume.

For a typical U.S. domestic online card payment, Adyen’s interchange-plus pricing may be cheaper, especially at higher volumes, but its total fee varies with the card’s interchange rate. For straightforward flat-rate pricing, Stripe is about 2.9% + $0.30 per transaction; PayPal’s standard card rate is about 2.99% + $0.49. ¹²³

So, Adyen may offer the lowest cost if you qualify and compare the actual interchange-based total; Stripe is a common simple, competitive option. Compare using your average order amount and actual card mix, and include any monthly, international-card, currency-conversion, or platform fees. These figures are U.S. examples; rates vary by region. ¹²⁵