To add an internal note in an invoice, follow the below steps.

1. Open the Moon Invoice application on your device or tap on this link.
2. Navigate to: Sales ➜ Invoice.
3. Select the invoice to which you want to add internal notes.
4. Tap on the Internal Notes option.
5. Enter your notes and tap Save.

Please note: Internal notes are for internal reference only and will not appear on the invoice PDF.