Is a flat rate or interchange-plus cheaper?

The short answer from the Reserve Bank's own data: a small merchant on a single-rate plan pays about 1.4% of card takings on average, and a small merchant on an unblended plan about 0.9%. Yet only 19% of small merchants are on unblended plans.^[1] Unblended is the RBA's word for interchange-plus. Whether it is cheaper for you depends on what cards your customers use and how much you take.

What each kind of plan charges

• Flat, or single-rate: one rate on every card. Zeller charges 1.4% in person on all cards, American Express included;^[3] CommBank's Smart terminal is 0.99% plus $29.50 a month rental.^[5]
• Blended: one rate for groups of cards, for example one for all debit and one for all credit.^[1]
• Unblended, or interchange-plus: the wholesale cost of each sale, meaning the interchange paid to the card's bank plus the card network's scheme fees, with the provider's margin on top. Each sale can cost a different rate depending on the card, the network and whether it was in person or online.^[1]

Why your card mix decides it

Cards don't cost the same to accept. Across all Australian merchants in the June quarter 2026, the average fee on eftpos was 0.43%, on Visa credit 1.00%, on American Express 1.36%, and on credit cards issued overseas about 2.95%.^[2] A flat rate charges a $10 eftpos tap the same as a tourist's credit card. A business whose customers mostly tap debit pays for the expensive cards in that average; one whose customers use premium and overseas cards gets a bargain.

Price the calculator's example mix (two thirds debit, 5% Amex, 3% overseas) at those averages and it comes to about 0.74%, against 1.4% flat. Treat that as the size of the gap, not a quote: the averages include large merchants on keen terms and come from before the October cuts.^[2]

The interchange cut reaches only one of them automatically

From 1 October 2026 the cap on domestic consumer credit interchange fell to 0.3%, debit is capped at 8 cents or 0.16%, and cards issued overseas get a 1.0% cap from 1 April 2027.^[1] On an unblended plan those cuts flow through to you automatically, because you pay the wholesale cost. On a single-rate or blended plan they reach you only if the provider lowers its rate, and about three quarters of Australian merchants, including most small ones, are on those plans.^[1]

When a flat rate still wins

• Lower volumes. Unblended plans are mostly used by large merchants and are rarely advertised.^[1] Stripe offers interchange-plus for large volumes,^[4] and Zeller quotes custom rates only above $250,000 a year in card payments.^[3] Below that, a flat plan may be the only one on offer.
• Many credit, Amex or overseas cards. A hotel or a tourist shop full of foreign cards can do well on one flat rate: overseas credit cards averaged about 2.95% across all merchants,^[2] against 1.4% flat at Zeller.^[3]
• Small sales with a per-sale fee. Some plans add a fixed fee to each sale: Stripe's in-person price is 1.65% plus 10 cents.^[4] On a $5 coffee those 10 cents alone are 2% of the sale.
• A predictable bill. One rate is easy to check and to budget for, which the RBA notes is part of why small merchants choose single-rate plans.^[1]

Decide in ten minutes

• Take your card mix from your statement; our statement guide shows where to look.
• Open the settings key on the calculator, switch to a rate per card type, and compare that bill with the flat plans it ranks.
• Ask your provider and one other for an unblended quote. Give them your monthly volume, average sale and card mix; they are the figures providers need for an accurate quote.^[1]

Debit-heavy and busy: get an interchange-plus quote. Low volume or full of credit and overseas cards: a good flat rate is hard to beat.