I'm glad in Canada, debit is tied to Interac which is a separate entity from Visa and Mastercard Debit which is targetted at people who want to make online purchases without requiring a credit card. So all debit cards work at Costco Canada, but in terms of credit cards, Costco Canada went with Mastercard. A little baffling why Costco USA and Canada went their separate ways when moving on from AMEX.