Supplier Portal Create Invoice process is calculating Taxes when it shouldn't be

Summary: Hello, I was wondering if anyone has any insight into why for some of our suppliers in a certain US State when invoices come in that should not be taxed and when these suppliers use the Portal to submit the invoices (as opposed to AP entering them in manually via Manage/Create Invoices) it is calculating taxes. It seems to work differently on the external facing Supplier Portal than it does when created internally.

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A few things. We use Vertex integration for tax calculation and not the Oracle configuration. Or in conjunction with Oracle. But it seems to be specific to only certain suppliers from one of our States that submits via the Portal. It does not affect other States/Suppliers. Also, to my knowledge our Vertex call only happens during the invoice Validation process.