PayPal Inc. is planning to turn off its PayPal Plug-In service, which lets users fund purchases at merchants that do not typically accept PayPal.

PayPal, a unit of eBay Inc., began e-mailing customers Monday to notify them that the service will be shut down Sept. 22.

PayPal Plug-In is a piece of software that generates a one-time-use virtual card number so that users can make purchases at merchants that accept MasterCard Inc. cards whether or not those merchants take PayPal.

The software also keeps a record of the card number in case it is ever needed again, and it lets users take screenshots of merchants' order confirmation pages to create a receipt archive.

PayPal Plug-In was introduced in late 2007 as an update to Virtual Debit Card, which also allowed purchases at merchants that do not take PayPal. Virtual Debit Card did not have the record keeping features that PayPal Plug-In has.

These record keeping features made Plug-In a more practical alternative payment method than Virtual Debit Card was. For example, a user would need to have a record of the one-time-use account number to request a refund.

PayPal's website told customers that it is discontinuing the Plug-In service because "it wasn't providing the best experience for those who used it." The tool may also be less necessary today because in recent years PayPal has become a more common payment option among large merchants.