Hi how can i add extra line in invoice hadder

Welcome to the Community, @theaussie57.

You can edit the invoice template you're using in QuickBooks Online (QBO) to add an extra line for the header. Please refer to these steps on how:

1. In QBO, go to the Gear icon at the top right to get to the Custom Form Styles.
2. Locate the invoice template you're using and tick the Edit option under the Action column.
3. Proceed to the Content tab, then click the Pencil (edit) icon on the header.
4. Place a checkmark on the ABN box to add an extra line.
5. Enter the necessary information in the desired field.
6. Hit Done to save.

To learn more about the process, consider checking out this article: How to add custom fields to invoices.

Please know that I'm only a post away if you have any other questions or concerns. I'll be here to assist. Have a wonderful day!