Hi there, Andre!

This happens when the Form Numbers option is not enabled on the invoice form style that you use. I can guide you to enable it so that you'll see the number on your actual invoices.

1. Open the invoice transaction.
2. Click on Customise at the bottom and choose Edit current.
3. Click the Content bar.
4. On the previewed invoice, click top section where you see the INVOICE#.
5. Place a check mark in the Form numbers checkbox.
6. Click Done to save the changes.

Let me know if you need anything else. Have a good day!