Tax code flow

Hi,

I have created a new tax code AA and in PO i have used this tax code when i will do GR and IR the tax code will automatically pick on the basis of PO, can any one explain me how does tax code flow from PO to MIGO and then MIGO to MIRO , if possible give table for Service entry sheet or GR and MIRO where i can view tax code is used.

Thanks & Regards

Kunal