For American Express cardholders, American Express offers a $15 statement credit when you spend $115 or more at Costco.com, via the Twitter #hashtag "#AmexCostco". That's the first such statement credit we've seen for Costco via American Express in more than a year. Limit one registration per customer. Sync and purchase must be made by December 31.
Note this is only valid on purchases made online at Costco.com and not in-store.