Can I change or exclude the account’s region reflected automatically in the header of invoices ?

Thanks for visiting the Community today, @financial4. I'm here to share insight about removing the region reflected in the invoice header. 

If you're using a different currency from your home currency, the one you assigned remains and cannot be changed nor removed. 

However, if you're referring to something else, you can edit the invoice header through customization. Here's how:

1. Go to the Settings menu, then select Custom Form Styles.
2. Select New Style, then select a sales form (invoice) type.
3. Go to the header section.
4. Edit the info in each field.
5. Select the checkboxes to add or hide the field.

For additional reference, check out this article: Customise invoices, estimates, and cash memos in QuickBooks Online.

Just in case, you can refer to this article should you want to personalize your sales forms: Import custom form styles for invoices or estimates.

Feel free to message again for your other concerns. I'd be here to help.