An invoice in WebMoney Transfer is a requirement for a WMID to pay a certain amount of WebMoney title units.
The user can issue and pay the invoice by using any WM Keeper.
Most often, invoices are used on websites for paying for goods or services and adding to their purses. This is possible thanks to the XML interfaces: X1 and X3.
WebMoney Transfer charges the same fee as for a usual transfer.
See also: Issuing invoices, Paying invoices, Cancel invoice payment, Sending invoices from WebMoney Keeper Standard, Issue invoice