Hello there, @mail45.
Welcome to the Community forum. Let me share details about how QuickBooks Online prints the customer's name on the invoice.
You'll want to review the Name to print on checks field on the customer's profile. It's possible that the old name was being set up from there.
Here's how:
- On the customers profile, go to the Name and contact section.
- Look for the Name to print on checks field.
- Edit the customer's name.
- Click Save.
Once done, reopen the invoice and check if the old customer's name is still showing on the Billing address section.
For additional reference, you can use the following article to personalise invoices in QuickBooks: Customise invoices, estimates, and sales receipts in QuickBooks Online.
Feel free to hit that Reply button if you have additional questions or clarifications. Have a great day ahead.