Tax classification code field at invoice line level

Hi Guru's

We are interfacing some invoices from ap_invoices_interface without any tax code and tax amount is zero.

On importing invoices to base table, invoice doesn't calculate any tax as expected but in ''Tax classification code'' field at invoice line level, tax code is populated.

Upon checking the default rules in tax manager responsibility i find tax code is defaulting from oracle payables financial options.

Could someone please tell me a way to keep this field blank in case there is no tax on the invoice.

Thanks in advance!!

Regards

Shivam