Question on Withholiding tax group

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Hi

I am trying to assign a Withholding Tax group to a supplier as default. However, i dont find any in the list of values.

I created the Withholiding Tax Rates from the screen :"Manage Tax Rates and Recovery Rates" screen by choosing withholding tax radio button. The WHT tax rates created are also visible in the ZX_WHT_TAX_CLASSIFICATION_CODE classification code. 

However i would like to understand if there is a difference in creating the WHT tax rate code from this screen or we need to create them from "Manage Tax Codes" screen. What is the difference between these two. Can i assign the WHT Tax rate codes to the Withholding group only if they are created from "Manage Tax Codes" ?