Hello there, @hopeful_sis.
I know a way where your customer can know their completed transactions.
In QuickBooks Online, you can always run Transaction List by Customer report to let your customer aware of their paid and even unpaid transactions.
You can use the Customize button to filter the details you need to show on the report. Then you can directly email this information to your customer.
I’ll show you how:
- Go to the Reports from your left navigation pane.
- Enter/select the Transaction List by Customer in the field.
- Click Customize, then select the date period.
- Under Filter, select what type of transaction and name of the customer.
- You can also select other details to show in the report.
- Hit Run report.
- Select the small envelope icon to email.

We also have Invoices and Received Payments report for completed and Open Invoices report for open transactions.
I also added this article as a reference in case you want to customize your sales form in the future. Through this, you can modify and personalize them base on your needs: Customize invoices, estimates, and sales receipts in QuickBooks Online.
Let me know if there are other things I can help you in QuickBooks. I'm always here to help. Have a good one.