Oracle payabales financial options where is set-up tax

Hi Team,

I am using oracle r.12.2.4

I would like to ask you if you can help me to find out what is is my predefined tax in Oracle Payables financial options.

Reason: My client wants to have new automatic way of uploading AP invoices. I have set-up in interface code to populate tax from supplier site level. as he assured me it is always same tax for 1 supplier, but it could be diferrent for various suppliers. path to set-this is: Find supplier> tax and reporting> Find the site you need for which ap is uploaded and click on update transaction tax. There is box :Tax classification. which has to be maintain by my client. But he asked me what if he forget to enter on some of his supplier tax.