The Pricing Model Question Nobody Explains Properly
Most Canadian merchants pick a payment processor based on the number in the sales rep's opening pitch, not the pricing structure behind it. "2.65% flat" sounds simple. "Interchange plus 30 basis points and 10 cents" sounds like homework. That gap in clarity is exactly how a lot of businesses end up overpaying by hundreds or thousands of dollars a year without ever seeing a red flag on their statement.
The honest answer to "which is cheaper" is: it depends on your card mix, your average ticket size, and your monthly volume. But it doesn't depend on guesswork. You can work out which model wins for your business with a calculator and last month's statement. Here's how the two models actually work, and where each one falls apart.
What Flat-Rate Pricing Actually Is
Flat-rate means you pay one percentage on every transaction, regardless of what card the customer pulls out. A basic Visa debit tap and a premium travel-rewards credit card cost you the same 2.6% or 2.9% under this model.
That sameness is the entire selling point. Processors like Square and Stripe built their businesses on it because small merchants without a payments background can budget for it without needing to understand interchange categories. One number, one line on the P&L, done.
The problem is that the processor isn't pricing charity. They're pricing the average of their entire merchant book, and pocketing the difference between what low-cost cards actually cost them and what they charge you. A basic debit transaction might cost the processor under 0.5% in real interchange. If you're paying 2.6% flat on that same transaction, the spread goes straight to the processor's margin, not yours.
What Interchange-Plus Actually Is
Interchange-plus (sometimes called "cost-plus") separates the bill into two pieces: the interchange fee set by Visa or Mastercard for that specific card type, plus a fixed markup that your processor keeps.
Interchange rates in Canada aren't secret. They're published by Visa and Mastercard and they range roughly from 0.3% to 0.5% for standard debit, up toward 1.4% to 1.9%+ for premium and corporate rewards credit cards. Your processor's markup sits on top of that, usually quoted as something like "interchange + 0.10% + $0.10 per transaction."
The advantage is transparency. You can see exactly what the card network charges and exactly what your processor charges, on every statement line. The disadvantage is that your total rate moves around depending on what your customers pay with. A business full of tap-and-go debit customers looks great under interchange-plus. A business full of premium rewards cardholders pays more, because those cards genuinely cost more to accept everywhere in Canada, not just with you.
Where the Math Actually Breaks in Your Favour
Say a Kitchener bakery does $40,000 a month in card sales, with a typical Canadian retail mix: about 55% debit, 35% standard credit, 10% premium rewards cards. Blended interchange on that mix usually lands around 1.0% to 1.3%. Add a processor markup of 0.15% plus a per-transaction fee, and the all-in effective rate often comes out to roughly 1.4% to 1.7%.
Under a flat-rate plan quoting 2.6%, that same bakery is paying an extra 0.9% to 1.2% of gross card volume every month for the convenience of not reading a statement. On $40,000 in monthly card sales, that's $360 to $480 a month, or $4,300 to $5,700 a year, sitting on the table.
Now flip it. Picture an e-commerce shop selling high-end electronics, where a large share of customers pay with premium travel-rewards or corporate cards because that's who buys $2,000 laptops. If premium cards make up 40% of volume, blended interchange can climb past 1.6% to 1.8% before any markup is added. Once you stack a processor's markup on that, the interchange-plus total can land close to, or occasionally above, a flat 2.6% rate. In that scenario, flat-rate isn't a rip-off, it's roughly a wash, and the simplicity might be worth it if your bookkeeping time has a real cost too.
The Variable Most Merchants Ignore: Ticket Size
Per-transaction fees matter more than most owners think, because they're fixed regardless of the sale amount. A $0.10 or $0.15 per-transaction fee is nothing on a $150 restaurant tab. It's a real bite on a $6 coffee.
A café doing 300 transactions a day at a $7 average ticket is paying that per-transaction fee on every single tap, whether the model is flat-rate (where it's often bundled invisibly into the percentage) or interchange-plus (where it's broken out as its own line). Low-ticket, high-volume businesses, coffee shops, quick-serve food, convenience retail, need to compare the per-transaction fee specifically, not just the headline percentage, because that fixed cost gets multiplied by transaction count, not dollar volume.
High-ticket, low-frequency businesses, contractors invoicing $8,000 jobs, healthcare clinics billing $300 procedures, feel the opposite pressure: the percentage rate matters far more than the per-transaction fee, because there are fewer transactions to spread fixed costs across.
Monthly Fees, PCI Fees, and the Line Items That Hide the Real Number
Neither pricing model tells the whole story on its own. Watch for:
- Monthly statement or account fees, typically $5 to $30, charged regardless of volume.
- PCI compliance fees, often $99 to $150 a year, sometimes billed monthly as $10 to $15.
- Batch or settlement fees, a few cents to a dollar per daily batch.
- Terminal rental, which can run $30 to $60 a month indefinitely if you never bought the hardware outright.
A processor advertising a razor-thin interchange-plus markup of "+0.08%" can still cost more than a competitor at "+0.20%" once you add up $25 a month in account fees, a $15 PCI fee, and a rented terminal you've been paying off for four years. Always ask for the effective rate, meaning total fees divided by total card volume for a real month, not the quoted markup in isolation.
How to Tell Which One You're Actually On Right Now
Pull your last three merchant statements and look for one of two patterns:
- If every transaction shows the same percentage regardless of card type, you're on flat-rate.
- If the percentage shifts transaction to transaction, higher on rewards cards, lower on debit, you're already on interchange-plus, possibly without knowing the markup you're paying above interchange.
If you can't tell from the statement, that's itself useful information. It usually means the processor prefers you not to look too closely.
A Rough Rule of Thumb
As a general pattern across Canadian small and medium businesses:
- Under roughly $10,000 a month in card volume, the admin time saved by flat-rate pricing often outweighs the modest dollar savings interchange-plus could offer, especially if your card mix skews heavily to premium cards.
- Between $10,000 and $50,000 a month, interchange-plus usually starts winning meaningfully, particularly for debit-heavy businesses like grocery, quick-serve, and personal services.
- Above $50,000 a month, the spread between the two models is large enough in dollar terms that it's worth negotiating markup directly rather than accepting either model's default pricing sheet.
These are patterns, not guarantees. A restaurant with high average tickets and a lot of tourist credit card traffic will behave differently than a hardware store with mostly local debit customers, even at identical volume.
What to Actually Do With This
Don't switch processors based on a percentage someone quoted you over the phone. Get your last three months of statements, calculate your actual blended rate under your current setup (total fees divided by total card volume), and compare that single number against a real interchange-plus quote built on your actual card mix, not a generic sample. The quote should show interchange rates broken out by card category, the markup on top, and every recurring fee, with nothing folded into a vague "processing fee" line.
Get a free side-by-side comparison of what you pay now vs PaymentsPlus at paymentsplus.ca/quote