Shops are finding the old-fashioned cash register expendable as the bulk of purchases are made with credit and debit cards, making having cash-on-hand obsolete.

Instead stores are beginning to have their salespeople armed with smartphones or tablet computers to register sales, and in some cases even the customers themselves will be able to load their purchase into their own mobile device.

The luxury retailer Barneys New York is planning on making the changeover this coming year, using iPads or iPod Touch devices to record purchases in seven of their almost two dozen non-outlet stores. Urban Outfitters, a clothing store chain for teen buyers, ordered its last cash register last fall. They plan to go completely mobile one day soon. Wal-Mart, which is the largest retail chain in the world, is now testing a “Scan & Go” application that allows customers to scan their purchases as they shop.

“The traditional cash register is heading toward obsolescence,” said Danielle Vitale, chief operating officer of Barneys New York.