Welcome to the Community, @restaurantexhust.

I’m here to share some information about adding a phone number on your customer’s invoice in QuickBooks Online (QBO).

Putting a phone number on customer’s invoice can be possible by adding a field solely for this information. However, you have to enter it manually each time.

Here’s how:
1.    Go to the Plus (+) icon and select Invoice.
2.    Select your customer.
3.    Click the small Gear icon on the upper right corner of the screen.
4.    Under Fields, click the + Add another field link.
5.    Enter Phone Number on the box.

The other option you have is to add it within the Billing Address section or the Return Address field. For more information, check out this article: Add a customer’s phone number in the sales transaction.

That should do it. If you need anything else, feel free to leave a comment below. I’ll be here to help. Take care and enjoy your day!