I want to look at the message I edited and sent with an invoice just over e a month ago. Anyone any idea how to do this?

You can open the sent invoice itself in QuickBooks Online (QBO), @denis5. This way, you'll be able to look at the edited message sent with an invoice and manage your transactions accordingly.

Let's locate the sent invoice transaction either in the All Sales or Customers tab and filter it from over a month ago. The All Sales tab list all your sales transactions. While the Customers tab lets you view the invoice by visiting your customer's Transaction List tab. For the All Sales page, here's how:

1. Go to the Sales menu.
2. Select All Sales.
3. Click the Filter button.
4. Choose Invoice in the Type field, then select all the other needed details (i.e. From and To dates, Customer, and Status).
5. Select Apply.
6. Locate the invoice, then select it to open its content.
7. In the Invoice page, go to the Message on invoice field to look at your message for your customer.

I've attached screenshots below for your reference.

You can also pull up the Sales by Customer Detail report. Then, customize it to filter all the sent invoices from over a month ago. Just go to the Sales and customers section from the Report menu's Standard tab.

Additionally, you can personalize your invoice email messages for your customers. In the Custom Form Styles window, go to the Emails tab. You can change the subject line, greeting, and message body. You can learn more about it by checking out this article's Personalize your email message section: Customize invoices, estimates, and sales receipts in QuickBooks Online. It contains the step-by-step guide in creating and designing your sales forms template.

Please let me know if you have other concerns. I'm just round to help. Take care always.