Wells Fargo & Co. is beefing up its business banking services with S1 Corp.'s automated clearing house product, S1 said Monday.

The Norcross, Ga., payments software provider's ACH service, part of its Corporate Banking product suite, replaces a service from ACI Worldwide Inc. that Wells Fargo previously used with its Commercial Electronic Office, or CEO, portal.

The San Francisco banking company decided to switch because Wachovia Corp., which Wells Fargo acquired, was using the S1 product for its corporate banking portal, Keith Theisen, an executive vice president and director of Wells Fargo's Treasury Management product team, said in an interview Monday.

"The ACI ACH solution has good ACH payment capabilities," Theisen said. "We just felt that the S1 solution had been a solution that Wachovia had been using already. It's a proven solution and it's been working well in their environment."

The S1 product already is being offered to new users of the Wells Fargo CEO portal, Theisen said. Wells Fargo is also preparing to migrate CEO users to the new service and will move Wachovia corporate customers from the Global Connect portal to CEO during the next 18 months, he said. "It will be an upgrade for the Wachovia customers also," he said.