Amazon.com will start managing subscription payments for start-ups and other companies - the latest in a series of quiet moves the e-commerce giant has made into PayPal's turf over the past year. The service, which launches on Monday, allows the company's more than 240 million active users to use credit card details stored on Amazon.com to pay for services such as a monthly phone bill or a digital music subscription. Amazon then charges a fee on each transaction. eBay's PayPal has long dominated online payments services but Amazon sees plenty of scope to push into new areas. The new service broadens Amazon's profitable role as a middleman for third-party sellers, which account for 40 percent of its sales and extends its influence beyond its website. It also comes ahead of June 18 unveiling by Chief Executive Jeff Bezos of what is widely expected to be a smartphone key to expanding Amazon's role in mobile payments.