I want to import customer notes into the Invoice

Yeah, the Notes is for the customer's profile only, but you can copy the content and paste it to their invoices. And, there's no way to import them.

The other option is to create an invoice template with a pre-entered note for each customer. The thing is you have hundreds of them, 

Thanks for choosing QuickBooks Online, SourBeer.

Custom form style lets you add additional information into your sales forms with less effort and time. You can add a custom field to be able to make the notes available on the form. Please follow the steps.

1. Click the Gear icon.
2. Select Custom form styles.
3. Go to the Content tab, then click the first part of the invoice on the other side.
4. Under the Display section, click Custom Fields.
5. Add Notes on the box, then place a checkmark on the box.
   
6. Click Done.

Once added, you'll see the custom fields box when you create an invoice. I've attached a screenshot for your visual guide.

Please check this article for the detailed steps: Customize Invoices, Estimates, And Sales Receipts In QuickBooks Online.

You can also record a single, partial, and joint payments in QuickBooks Online. Here's an article that you can visit for future reference: Record Invoice Payments in QuickBooks Online.

If there's anything that you can help us with, let us know so we can further assist you.

So this Notes field on the invoice will pull up the data from the Notes field in the Customer Information section? I doubt it...

This will not pull in information from customer notes. Also the box will not allow for any reasonable amount of text to be place inside of it.

Thank you for getting back, @SourBeer.

Let me share additional information about invoices and customer's details. Yes, the data from the Notes field on the Customer Information window is only on the customer's profile and won't display on the invoice. The workaround given by MariaSoledadG above is to add a customize field from the Custom Form Styles then enter the elements from there. However, the amount of text or information you can add from there is just limited. This way, you may input the notes on the Description field when creating invoices.

I understand the importance of importing the customer's notes into the invoice. Rest assured our engineers never stop to develop QuickBooks to deliver the best experiences for all of the QuickBooks users. Hopefully, they'll consider the request in the future.

At this time, you can visit our blog to stay current with the latest QuickBooks news and feature updates.

As you continue working with invoices, you can also read the topics from this link in case you want to send and print them for your customers in the future: How to email or print an invoice.

Please post again in the Community if you have additional concerns. I'm here to keep helping. Keep safe!