How can I customize my invoice form to display customer phone number? I don't know why this answer isn't easy to find on the Help knowledge base. QuickBooks Online, 3/24

I've got you covered, @KeikoCat. Let me guide you on how to add a customer's phone number to the invoice in QuickBooks Online (QBO).  

In QBO, you can utilize the Custom field feature to add other information to the invoice display template. To add one, you can follow the steps below:

1. Go to the Gear icon, then select Custom fields.
2. Click the Add field button, then enter the name of the new custom field.
3. Tick the box for All Sales forms where to show this field.
4. Toggle on Print on form to include this once you print the forms.
5. Once done, click Save.

Once you are done with these steps, you can easily enter your customer's phone number when you create and send an invoice to them.

For more details on managing your custom fields, here is the full article: Manage custom fields in QuickBooks Online.

Furthermore, you go through these articles below if you need more help customizing your forms: 

• Customize invoices, estimates, and sales receipts in QuickBooks Online.
• Add, customize, or remove logos on sales forms.

You can always add a reply below if you have an additional concern about customizing your invoice and other QuickBooks-related tasks. I'd be glad to assist you further. Have a good one!