It's a pleasure to see you here in the Community, @989.
I can help you add your company phone number to invoice in QuickBooks Online (QBO).
To make your phone number shown on the invoice, you will customize or edit the template. Let me show you how:
1. Click the Gear icon at the top, then pick Custom Form Styles under Your Company. 2. On your invoice template, select Edit under Action column. 3. Go to the Content tab, then click the Pencil icon on the right. 4. Make sure that you choose the Header. 5. Put a check mark on the Phone under Header, then enter your company phone number. 6. You can click Preview PDF to check. 7. Select Done.