A: Partial invoicing is done in Fortnox. In Upsales you can view the remaining balance of the invoice. This requires Fortnox Premium, with Modul att synka set to Faktura or Order & Faktura.
Then select Aktivera Saldo på faktura under Extra fält in the Fortnox Premium settings. Upsales adds an order field called Saldo, which shows the invoice's remaining balance and is updated each time the invoice syncs from Fortnox.