There are 2 ABN numbers showing on our invoices?

It's nice to have you in the Community, @abbycooper_5.

To further isolate the issue, let's go to the Custom Form Styles page to check if there are two ABN's entered in the Content tab on the invoice template.

Here's how:

1. Click the Gear icon at the top, select Custom Form Styles. 
2. Choose the invoice template and hit Edit under the Action column.
3. Go to the Content tab and click on the Header.
4. Make sure the ABN box is checked with the correct number.
5. In the Display section, uncheck the custom field which contains other ABN number.
6. Select Done.

For your visual reference, see below screenshots:

Once finish, try to create an invoice again. Check to see if it's showing one ABN only. 

In case you need tips in the future, visit our QuickBooks Help Articles site. 

Stay in touch with me if you any other questions by adding a comment below. I'm always here for you. Have a great day!