Payment Method details can only be created or updated for R12. If there is no ‘Bill To’ business purpose, the Site form will allow you to enter a payment method. But when you close the form, the details will not be written to the worksheet.
In 11i the Customer and Site forms will not display a Payment Method tab (even if the columns are in the worksheet) as these details can only be uploaded for R12. If you enter the payment method details directly into your worksheet and upload the details these will be ignored by the interface and no error message will be returned.