Didn't setup vat code in supplier but on PO Manage Tax page, vat always default.

Hi everyone,
I didn't setup vat code in supplier and either or supplier site. But when I create PO and review on Manage Tax page.
The vat code always there as the default. When I tried to match at AP invoice, this vat was calculated also.

Anyone know where can I check this problem? I don't want the vat code is default in PO because I didn't set it at Supplier.
I want it default only that I set in Supplier.

Thanks,
Kams