American Express will limit the way its Serve customers can load money on to the “full-service” prepaid banking platform.

Amex disclosed yesterday that it will no longer allow Serve customers to use non-American Express credit cards to load cash on to Serve, which is effectively an online banking service, much like Amex’s Bluebird product. The change will go into effect on April 16.

Instead, only American Express Cards are eligible for adding money to Serve accounts. That means Discover, Visa or MasterCard credit cards will no longer be available to Serve customers. Those cards are no longer eligible as “backup funding” sources either, Amex said.

Still, beyond using Amex cards, Serve customers can upload money via:

• Direct deposit;
• Cash at CVS/pharmacy, Walmart, some 7-ELEVEN stores, among other retail locations;
• Purchasing the Reloadit service;
• Check; or
• Bank transfer.

The announcement is important, because Serve had been positioned as something of a bank account replacement by Amex. The change in policy will obviously now limit Serve to the American Express network.

American Express did not offer an explanation for why it will implement the change.