Canadian merchants have a structural advantage most of the world doesn't: Interac, a domestic debit network that charges flat cents per transaction instead of a percentage. Every sale is therefore a choice between two completely different cost structures — and the math of that choice is decided by one number: your average ticket.
The two cost structures
Interac debit: flat cents. Interac charges no percentage-based interchange at all. Standard chip-insert transactions carry zero interchange; contactless (Flash) transactions carry a small per-transaction fee. Typical all-in merchant cost: $0.02–$0.08 per transaction, regardless of whether the sale is $5 or $500.
Credit cards: a percentage. Typical merchant costs: basic cards 1.40%–1.70%, premium rewards cards 1.75%–2.40%, Amex 2.30%–3.50%. A worked example on a $100 premium Visa sale: 1.85% interchange + 0.15% network assessments + 0.20% processor markup = $2.20, or 2.20%. The fee scales with the ticket — a $400 sale costs roughly eight times a $50 sale.
The crossover: worked at two ticket sizes
Illustrative crossover (assumes Interac at $0.08/transaction and credit at 2.0% effective — plug in your own statement's numbers): Interac costs $0.08 whether the ticket is $15 or $150. Credit costs $0.30 on a $15 ticket and $3.00 on a $150 ticket. The breakeven is a $4 ticket — above $4, debit wins on every single sale, and the gap widens with every dollar: $0.22 saved per $15 sale, $2.92 saved per $150 sale.
Now scale it to a month. A café doing 10,000 transactions at a $15 average ticket with a 70/30 debit/credit mix: Interac costs 7,000 × $0.08 = $560; credit costs 3,000 × $15 × 2.0% = $900. Total: $1,460/month. A furniture store doing 2,000 transactions at a $400 average ticket with a 50/50 mix: Interac costs 1,000 × $0.08 = $80; credit costs 1,000 × $400 × 2.0% = $8,000. Total: $8,080/month — and shifting just 20% of those credit sales to debit saves roughly $1,584/month. High tickets are where the mix becomes real money.
Interac's real fees: chip vs Flash
The network fees behind those cents, so you can read your statement: chip-insert Interac transactions carry zero interchange — the cheapest payment in Canadian commerce. Contactless Flash transactions carry tiered fees: $0.020 (low-ticket merchants), $0.025 (high-volume), $0.035 (all others) on transactions from $0.01–$100, and $0.055 on $100–$250. Interac's card-brand fee is $0.0158 per transaction. Your processor adds its margin on top — which is why the all-in number lands in the $0.02–$0.08 range rather than at the network fee itself.
What shifts the mix (and what's off-limits)
What works: simple, visible nudges. "Prefer debit? We accept Interac" signage at the till — Interac itself promotes merchant signage for this. Making payment options visible and easy rather than defaulting every customer to the credit terminal. Training staff to present the terminal neutrally instead of steering. None of this costs anything, and on high-ticket sales it pays immediately.
What's off-limits: you generally cannot surcharge debit transactions — several networks don't allow it, so check with your processor before assuming. And don't build the strategy around refusing credit: a customer who only has credit and gets turned away costs you the entire sale, which dwarfs any per-transaction saving. The pattern from several processor migrations applies here too — the expensive mistake is never the fee you can see, it's the revenue you never realized you lost.
When to bother: high average tickets, thin margins, and high volume — furniture, appliances, auto repair, B2B. When not to: low-ticket, high-speed environments where the absolute saving per sale is pennies and throughput is the business — a busy lunch counter gains little from a debit crusade.
A note on format: this is an explainer, not a procedure — there are no step-by-step actions because the question it answers is which setup fits your business, and that is what the comparisons above are for.
FAQ
How much does Interac cost a merchant per transaction?
Typically $0.02–$0.08 all-in. The network itself charges zero interchange on chip-insert transactions and $0.020–$0.055 on contactless Flash transactions by merchant tier, plus a $0.0158 card-brand fee — your processor's margin makes up the rest.
Can I surcharge debit transactions in Canada?
Generally no — check with your processor, because several networks don't permit debit surcharging. Credit-card surcharging has its own separate rulebook (2.4% cap, advance notice, disclosure requirements).
Should I encourage customers to pay by debit?
Yes, with light-touch signage and neutral terminal presentation — especially on high-ticket sales where each shifted transaction saves dollars, not cents. But never force it: turning away a credit-only customer costs the whole sale.