Hello there, @akwh.
Let me guide you through the steps to resolve this issue.
While the ABN details in the GST tab are already correct, let's refresh the system by removing the information, leaving the field blank temporarily. Then, re-enter the ABN and save the changes. Once updated, try drafting a new invoice and preview it to check if the issue has been resolved.
If the issue persists and your customer's ABN still appears on the preview or saved invoice, please reach out to our live support team for further assistance. They will investigate the underlying cause and help resolve the issue.
Let us know if you have more concerns regarding QuickBooks. We're always here to help