When running any kind of Journal Entry transaction code (FB50, FV50, etc), where it is going across multiple company codes, I am getting a "First Posting Item Is Not In Leading Company Code" error. Although it shows as a green informational message, it is actually a hard stop that does not allow me to proceed unless the first line is from the leading Company Code.

Solution:

This change is effective with Enhancement Pack 4 (EHP4) for ERP 6. 

According to SAP Note 1387675, the company code in first posting line must be same as the leading company code. The associated error message, F5A 296 cannot be suppressed or customized. If you get this error, you must change the first line item entry of the journal item to the leading company code.

In a typical FB50 / FV50 recording with Transaction, you would enter in each line item in row 1, select that first row, and then hit the insert row button. This set of actions is put into a loop so that all line items are entered in the first row. If you are running into this problem with the implementation of EHP4, you must make the following changes to your recording:

• The first line item needs to be entered, outside of the loop (on the header level), on row 1. This first line item must be from the leading company code. This will have to be a training issue for those filling out the Excel sheets.
  
• The subsequent line item entries need to be entered on row 2, then row 2 is highlighted, then the insert row button is hit. This set of actions is put into the loop so that all subsequent line items are entered in the second row.