Hi Bjørn,

It is for internal notes only, at least with the standard invoice report.  To illustrate this, I added an invoice note to an existing order before invoicing and this is visible in the UI (also after invoicing, it is visible)

The standard invoice report does not show the invoice notes:

By default, it is hidden.  I suppose, though I have not tried this, you can create a customer invoice report to add this value but in your case, it likely will not also be added to the output to your staging database as this is a custom development since you do not deliver invoices from Alliance to your customers.

Thanks, Phil