How do I get the customer telephone number to display on all invoices?

Welcome to the Community, @dianne6.

In QuickBooks Online (QBO), there isn't a direct way to get the customer telephone number display on all invoices. However, there are two workarounds that you can do to achieve this.

The first one is to add the telephone number to their billing address. This way, it'll automatically show in the invoice once the customer is selected. Here's how:

1. In QBO, go to the Sales menu at the left pane to get to the Customers page.
2. Select the customer's name, then tick Edit at the top right. 
3. In the Billing address section, add their telephone number.
4. Hit Save. 

For more information, please refer to this article: Edit customer information.

The second option is to add a custom field to the invoice. However, you'll need to manually enter their phone numbers every time. Consider checking out this article for the detailed steps on how: How to add custom fields to invoices.

I'll pass along your suggestion to our Product Developers. They're always looking for ideas to consider on how to improve QBO. In the meantime, I recommend visiting our Blog site. This is where we share recent happenings and future developments, such as updates to newly added features.

Reach out to me in the comment section below if you have any other concerns. I'm always here to answer them. Have a great day!