What Interac actually is
Before getting into deposit flows, it's worth knowing what you're actually using — Interac isn't a "casino payment method" that was built for gambling, and understanding what it is explains most of why it behaves the way it does at a cashier.
A Canadian-owned payments network, not a card network
Interac Corp. is a Canadian company jointly owned and operated by the country's major banks and credit unions as a shared payments network. It's the same system behind Interac Debit at a store checkout and Interac e-Transfer between two people — a casino cashier offering "Interac" is plugging into that existing national network, not a payment product any operator built itself.
How it differs from Visa or Mastercard rails
A card payment routes through a card network's authorization system, with your card number and a merchant category code attached to the transaction, and a chargeback mechanism sitting behind it. An Interac transfer moves directly bank-to-bank instead — no card number is ever generated or shared, and the transaction looks, from your bank's side, essentially identical to sending money to a person. That structural difference is why the two payment types behave so differently at a casino cashier.
Why it became the default for Canadian online gambling specifically
Many banks and card issuers apply merchant-category-code flags to gambling transactions on credit cards, which can mean declines, cash-advance treatment, or outright blocks regardless of which casino you're using. Interac transfers aren't classified or processed the same way, since they move as a standard bank-to-bank transfer rather than a flagged purchase category. That difference is a large part of why Interac became the practical default for Canadian players well before "everyone already uses it" was true on its own.
A cooperative that's forty years old, not a startup
Interac Association was formed in 1984 by five Canadian financial institutions — Royal Bank of Canada, Scotiabank, CIBC, TD, and Desjardins — to build a shared cash-dispensing network that worked the same way at every member's machines. Bank of Montreal, Canada Trust, Laurentian Bank, National Bank, and Credit Union Central of Canada joined within two years, and membership kept growing from there. Interac Corporation, the single for-profit entity that now runs the network, wasn't created until February 2018, when the original non-profit association merged with Acxsys, the for-profit affiliate the same member institutions had set up in 1996 to build newer services — Interac Online among the first of them — on top of the core network.
Today the network counts roughly 83 member banks and credit unions, and Interac reports more than 20 million transactions moving across it every day. That scale is why a casino cashier can simply say "Interac" and expect it to work no matter which institution you bank with, instead of building a separate integration for each one.
Debit before transfers: how the network actually grew
Interac Direct Payment — the point-of-sale debit product most people now just call "using your debit card" — started as a pilot in Ottawa in 1990 and rolled out nationally in 1994, years before Interac did anything resembling an online transfer. It caught on fast: Canadians ran a billion Direct Payment transactions through it in 1997 alone, and by 2000 debit had overtaken cash as the payment method Canadians used most. That adoption curve is part of why a "Canadian bank transfer" defaults to Interac by reflex now — the network had already trained a generation of Canadians to trust it at the till years before online casinos existed to accept it.
e-Transfer's real launch date, and what came after it
Interac e-Transfer — the product actually doing the work at most casino cashiers today — launched in 2003, run by Acxsys on top of the core network rather than replacing it. Interac Flash, the contactless tap product, came later still: a small pilot in downtown Toronto in 2009, a proper national rollout on debit cards starting in 2011, and by the mid-2010s most Canadian-issued debit cards could tap. None of that changes how a casino deposit works today, but it explains why "Interac" at a cashier can mean a couple of different underlying products depending on which one your own bank still supports — covered next.