Hi,
Much or the invoice process / basic data can refined / additional records set up.
For example, you can duplicate the series ID and call it something meaningful for your needs.
Similarly, the invoice type can be duplicated, and name it something meaningful. The new invoice type can have the series ID you just created.
Additionally, the external supplier invoice parameters can have a different load type, driving a different invoice type.
The key to this would be to assign a different invoice type driving a different invoice series.
Are you loading the invoices via a file _ external supplier invoice assistance? Sounded like you were using some other way for the invoice loading.
In any case, try loading a different invoice type (the one you created per the above), and that would drive the series.
Best regards,