This weekend marks the official end of Costco‘s longtime partnership with American Express as the company begins a new relationship with Citibank Visa. The Costco Amex was known for its generous cash-back rewards program, but the Costco Visa raises the bar even higher: 4% cash back on gas purchases, 3% on restaurants and travel, 2% at Costco and 1% on everything else. American Express, which stands to lose nearly 10% of its customer base with the dissolution of the Costco deal, is now trying to lure back lapsed cardholders with a sweet $250 cash-back offer. For an informative Motley Fool report on the benefits of both cards, click here. And no matter what you decide, this Sunday (June 19th) is the last day that any kind of Amex card will be accepted at Costco.