PO BU's used for multiple countries with Different VAT

Example.  I have a PO BU 10000 in Shanghai China.  I am entering a PO for a ship to and vendor in Tokyo Japan.  The issue is that although I can get most of the VAT settings to reflect Japan, I can't get the reporting country to reflect Japan therefore the VAT registration ID on the PO and amount is China.  And I can't change the VAT reporting country to JPN it only gives me the choice of CHN.

Has anyone dealt with this and how to set up VAT correctly?