Here is the situation

Example I sell to the customer
Tax base amount      : 100.000
Income Tax              :    4.000
VAT                         :  10.000

The journal for that transaction is :

For cash payment
Dr  Bank                             106.000
Dr  Prepaid Income tax            4.000
Cr  Sales                                        100.000
Cr  VAT Out Payable                          10.000

Example I buy  from the supplier
Tax base amount   : 100.000
Income Tax           :    2.500
VAT                      :  10.000

The journal for that transaction is :

For cash payment
Dr Inventory              100.000
Dr Prepaid VAT In         10.000
Cr Bank                                 107.500
Cr Income tax payable                2.500

For the VAT I think I can use the tax item no problem with that.

But for the Income tax I think I must use the tax group but I haven't found a way to get what I want. Each customer/supplier will have different percentage of income tax that related to good/service they bought/sell according to our tax law. The income tax is reducing the amount I pay to the supplier or the amount I get from the customer. On the COA I have create the separate tax account for every tax.

So how to setup the tax group to accomplish that?
Thanks for the answer and BTW when is the 2.3 final will release? Cant wait