Use it to pay down your renewal. By some steaks or lobster
You can buy anything in costco with that but only in costco or online for costco
A certificate is usually from the 2% you're getting back from being a executive member or a credit card holder you can use like cash when u pay or redeem it at the customer service counter
If it's a Costco gift card, it should be good. I'm not sure what a Costco certificate is.
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