Thanks for getting back to us here, @jdolan14.

I have some information about adding an internal note to your report. The A/R Aging Detail report has an embedded filter that excludes transactions that don't affect Accounts Receivable. That said, you can use the Memo field on your invoice as a workaround to add your internal note. Then, add the memo field when you pull up the A/R Aging Detail report. 

Here's how to do it.

1. In your Home Page, tick Create Invoices.
2. Enter the invoice details.
3. Scroll down towards the Memo section. Type in your internal note.
4. Hit Save & Close.

After creating the invoice, open the A/R Aging Detail report and add the memo field. Here's how:

1. Go to Reports at the top, and then select Customers & Receivables.
2. Choose A/R Aging Detail. Then, snap the Customize Report button.
3. Type Memo in the Search Columns field, and then put a check mark before it.
4. Click OK.

With these steps, you're able to view your added internal note from your invoice and into the report. You can check out this guide for more information about customizing report: Customize reports in QuickBooks Desktop.

In case you need help with other report tasks, click this link to go to our general report topics. It has articles that'll walk you through the process.

Keep me posted if you have other questions or concerns. I'm more than happy to assist you. Take care and have a great day ahead.