Yes, you can track notes directly on your customers' invoices using the Note to customer field, billing104. Let me walk you through the step-by-step process below.
Recording special circumstances, agreements, or concessions on your invoices provides a crucial written record, helping resolve potential discrepancies and ensuring consistent customer service in future interactions.
To add a personal note to your customer's invoice, here's how:
- Head over to the Sales section and click on Invoices.
- Select the invoice you want to update and click on Edit Invoice.
- Scroll to the Note to Customer field, where you can type your message.

- After adding your note, make sure to click Save and Close to apply the changes.
Also, take a look at this attached article that delves into managing invoices in QuickBooks Online (QBO): Understanding Invoices in QuickBooks Online.
To better assist you with managing your invoices in your future task, I'll attach these articles for reference:
Furthermore, please check out our QuickBooks Live Expert Assisted team if you need further help identifying the report you can generate depending on your business needs. They can also assist you in understanding how each of them works and the data it contains.
I am available whenever you need assistance with managing your invoices. Please know you can always come to us or save this thread by circling us back, and we'll assist promptly.