Hello lorgayle2-gmail-,
It's a pleasure to see you in Community. Welcome! QuickBooks Online is a dynamic program, with the features you need to accomplish your daily bookkeeping tasks. I can understand the importance of internal notes on your sales forms. I would be glad to help!
QuickBooks Online offers the option to create custom fields for your forms. The can be created with the option to have them visible on your forms, or private.
Follow these steps to add them to your invoices:
1. Open your Settings ⚙ and select Account and Settings
2. Choose the Sales tab on the left menu
3. Click the Edit in the Sales form content field
4. Hit the link to add Custom fields
5. Give it a name and select the Form type
6. Leave the Print on form option to the off position
7. Once you're finished hit Save.
If you have any other questions, feel free to reach out. We would be happy to assist!