Classify purchase as Goods/services for tax calculation

Summary

Looking for system options to classify a purchase as Goods / Services. This is primarily from a tax calculation perspective

Content

Hi!

Here is a question on Use taxes accrual for Goods vs Service

Some of the items purchased will require use taxes to be accrued. This is when Supplier doesn't include sales taxes on their Invoice. 

The requirement is that Use tax should be  accrued only if we purchase goods. How do we flag a purchase as Goods or Services on the PR/PO flow? We don't use Inventory module. We use Purchasing Categories.

Thank you!