Hi Babu,
Changing the tax code is not possible, coz all the dependency PO will get affected.
I Suggest you to go with creation of new tax code V0. Maintain all the condition type defined for VO. Assign all the corresponding G/L in OB40 for the tax code V0 by checking the accrual key's condition type for the tax procedure in OBQ3.
Regards,
Ganesh