In TriFact365 it can be set that the booking number of a sales invoice is seen as the invoice number.
Go to Settings (Cogwheel) and click on Administrations. Click on the Pencil behind the relevant accounting record.
Go to the blue Settings tab and check the box next to Invoice number is entry number with sales invoice and click Save.
This setting is only available for AFAS, Exact Online and iMUIS Online.