Hi there, @heart-stone-pm-c.
I can see how a customer portal would be helpful. It would allow your clients to view their invoice history and update their contact info. QuickBooks Online offers the support of various third-party apps for any functionality you may need. To look for an app, head to the Intuit App Center and type a keyword in the search bar.
You can follow these steps:
- On the left panel, click Apps.
- Go to the Find Apps tab.
- Type in "Customer Portal" in the search bar.

Refer to these articles for more info:
Stay in touch if you have any other questions or concerns. I’ll be right here to answer them for you. Enjoy the rest of the day.