How is the Taxcode determined for invoice main/sub maintained in ACCINF if those main/sub are not maintained in EK02

Hi Experts,

Well I have a situation, where the FICA doc posted for an invoice has main/sub coming from "ACCINF" line item. i.e. the one we maintain at following config SAP Utilities->Invoicing->Invoice Processing->Item Selection in Invoicing->Item Selection in Account Maintenance/ Define Sub-Items.

But this main/ sub is not mentioned in EK02 or TFK033D , then how is the tax code determined for this main/sub in the document..?

PFA the attachment.

Thanks in advance.