To display your tax number (ABN, VAT and so on) in the headers of storefront invoices, you can use the following mod. It involves adding custom translated labels and editing Ecwid CSS theme.

In the following code replace the ABN and the long number with proper name and your number. The resulting code needs to be added into the page that currently has your Ecwid store embedded.

Note: If you already have custom translated labels in your page, then this new code must be added after your existing translation code.

Then to your Ecwid CSS theme add the following snippet, that will visually center your number in the invoice header:

This will display your tax number in the center of the invoice header both in the displayed and printed order invoices for your customer: