@Micha_Brief Ah, no, Tax Codes aren't adjustable within the Expensify interface when you've connected the NetSuite integration, as Ted said above.
Tax rates in Expensify do not have a GL Code. You can surface a Tax Name, Tax Rate and Tax Code:
However, Tax Codes aren't available when you've connected to NetSuite:
When I sync it to Netsuite I receive a wrong tax code, Is there a way to change it from expensify side?