QXL's auction winners will be encouraged to use FastPay to pay for their goods as part of a commission-based deal that will see QXL earn revenue each time one of its members registers for FastPay.
Available to use for all auction and classified transactions, Fast-Pay will be pushed throughout the QXL site via banners and section placements.
It will also be promoted within emails to QXL members.
NatWest will push its partnership with QXL on the FastPay site (www.fastpay.com) in the form of a promotional page detailing the service's features.
Tipped last month in Revolution (6 November, p3), QXL's appointment of an exclusive online payment provider follows eBay's decision to roll out a UK version of its PayPal payment service in October.
"This is important for us," said Craig Carr, business development manager for Europe at QXL. "We've been looking at all the players over the past few months, including both Nochex and Egg Pay."
He added that the auction site could extend the scope of its partnership with NatWest and roll out the FastPay relationship across some of its 11 other European sites early next year, depending on the performance of the UK site.
"We may well look to seed our other sites with FastPay," said Carr. "The service allows users to pay with euros as well."
QXL's tie-up with NatWest represents the latest development in an increasingly active online payments market.
Earlier this month, NatWest revealed it would allow its users to send payments to recipients via their mobile handsets.
Yahoo! UK & Ireland, meanwhile, tied up with high-street bank HSBC to launch an email-based payment service called Yahoo! PayDirect from HSBC (Revolution, 13 November, p3).
The Yahoo! service will look to compete with the likes of Egg Pay, the online payment service developed by web bank Egg.