Is it possible to add notes to an invoice and have that information hidden from the customer? For example, if I wanted to put some billing info for future reference

Hi Sue5,

Thanks for posting in the Community!

If you're subscribed under the QuickBooks Online Essentials or Plus version, you can turn on the Custom field to add a notes section. Let me guide you on how.

1. Click on the Settings icon, and click on Custom fields.
2. Click on Add field or Add custom field.
3. Enter a Name for the custom field.
4. Tick All Sales form, Purchase order, or both.
5. For internal notes, don't turn on Print on the form.
6. Click on Save.

Once done, open an existing or a dummy invoice and the new field you created will appear for you to enter internal notes visible only to you. Just a heads up that custom fields have limited characters only up to 30 characters.

You can check this link to learn more about custom fields: Add custom fields to sales forms and purchase orders in QuickBooks Online.

Post again in the Community if you have more questions!