THANK YOU I GOT THE ANSWER :-) Does Costco except credit card as a source of payment or just debit card?

Any Visa card works. However, you'll need to show either your membership card or your Costco visa card to get into the store, then at the register you can pay with any and only visa cards if you're paying by Credit. HTH.

Costco takes any Visa as payment from a member, not just Citi Visa.

See Abhi response

All debit cards and ONLY COSTCO VISA credit card

Credit card works