Invoice numbers are identifiers that are assigned whenever an Invoice is created.
By default, an Invoice number begins with a prefix followed by numbers that go up in sequential order as Invoices are created.
Depending on your Invoice Settings, the Invoice number may be adjusted at the time of creating the Invoice, or at any stage within the Invoice
Additional Information
The Invoice prefix is predetermined by your system admin
It is recommended that Invoice numbers are kept unique for easy identification, however, it is possible to have more than one Invoice with the same number if needed.