Product version:
iVend 6.6 update 0 with SAP B1 version 9.3
Problem statement:
While accepting the goods receipt then it shown error

“Tax Code is not defined”.
Proposed Solution/Workaround:

While accepting the Goods Receipt and user want to accept the product without tax applicable then the field "Tax Exempt" it should be checked on Product master screen. For reference, check the below attachment.