Hi, 

From a Finance perspective (IFS Finance) this is all driven based on posting control. Posting control reviews s business transaction and then creates a posting string / code string.   The settings are all configurable.  So no one attribute (for all clients) would drive a code string. 

A purchase order will result in multiple posting lines. For example, if the PO line is for inventory, you will have an inventory posting. If the PO is not non inventory, then you will see other. 

Assuming you're in a TEST environment, receive a PO line. Then immediately go to the screen below. Search for the most recent records (by accounting ID).  This will display accounting information. 

The most important thing for this question is to see the posting type.  For example, M91 for a non-inventory receipt. 

Then see the posting control and search for the M91.  This lists “how” the code part values are derived. 

The Exception would be if you use what we call - ”pre-posting”. That would be a situation where you “‘manually” enter a cost center for example on a PO line.   We have different flavors of pre-posting and they all affect things differently. Tha basics are the same just a little different. 

In short, it’s all configurable, and we can back track to see exactly what drives what based on the transaction and what was configured in posting control.  See the posting type. Then the rules in posting control for a given posting type. 

Best regards.