When setting up tax rates in Fusion, where do you set the GL codes up? Usually you can use the recovery rate to drive the AP GL account codes and autoaccounting to drive the AR GL account codes so why do we need to put any GL codes on the Tax Rate itself?

The reason is that if you are using self-assessed taxes instead of offset taxes then you need to set these values. Make sure however that your liability account is set up as a liability account or it will not be accepted.

Oracle Fusion Tax Rates

Oracle Fusion Tax. Tax Rate setup, Tax liability account and Tax Recoverable Account