How do you disable Tax Rate Override in Invoice creation?

Business wants to disable the Tax Rate Override drop-down in Invoice level to avoid risk of changing the default tax.

Default tax rate was assigned at the Supplier level.

We have unchecked the following, but still able to select and assign different tax rate:

1. Manage Taxes - Allow override of calculated tax lines and Allow entry of manual tax line
2. Manage Tax Statuses- Allow Tax Rate Override