Symptoms

In the derived Invoice document skill, the built-in rule Check LI Total Prices against Total Amount is enabled. However, no error is thrown if the Total Price is empty:

Cause

The error is not being shown because of the condition in the script rule:
 

 
In the sample above, there are two line items with the Total Price being empty for both of them. So, the comparison is not run.

Resolution

If it is required to check the column is not empty, then it is possible to make the Total Price column required.

• In the skill editor, just right-click on the required column and go to the Column Settings:
  
  
  
• Enable the Required field option: