Code Behind “How to Prevent Negative Inventory” – Versions After 2013

 PreventNegativeInventory() : Boolean  
 CASE "Prevent Negative Inventory" OF  
  "Prevent Negative Inventory"::Yes:  
   EXIT(TRUE);  
  "Prevent Negative Inventory"::No:  
   EXIT(FALSE);  
  "Prevent Negative Inventory"::Default:  
   BEGIN  
    InventorySetup.GET;  
    EXIT(InventorySetup."Prevent Negative Inventory");  
   END;  
 END;  

But this is not the complete one, we need to find other places where this function is been called. So I went back to “Statical Prism” and search for the PreventNegativeInventory function usage.

As shown in the above picture  PreventNegativeInventory function is called from Item Ledger Entry Table

 VerifyOnInventory()  
 IF NOT Open THEN  
  EXIT;  
 IF Quantity >= 0 THEN  
  EXIT;  
 CASE "Entry Type" OF  
  "Entry Type"::Consumption,"Entry Type"::"Assembly Consumption","Entry Type"::Transfer:  
   ERROR(IsNotOnInventoryErr,"Item No.");  
  ELSE BEGIN  
   Item.GET("Item No.");  
   IF Item.PreventNegativeInventory THEN  
    ERROR(IsNotOnInventoryErr,"Item No.");  
  END;  
 END;  

As in the code this is not the complete code, to find out the missing part open up the “Statical Prism” and search for VerifyOnInventory function usage. 

There you go, In the “Item Jnl.-Post Line” Code Unit under InsertItemLedgEntry function it calls for VerifyOnInventory function and it trigger the entire process. Following is the function code. 

 LOCAL InsertItemLedgEntry(VAR ItemLedgEntry : Record "Item Ledger Entry";TransferItem : Boolean)  
 WITH ItemJnlLine DO BEGIN  
  IF ItemLedgEntry.Open THEN BEGIN  
   ItemLedgEntry.VerifyOnInventory;  
   IF NOT (("Document Type" IN ["Document Type"::"Purchase Return Shipment","Document Type"::"Purchase Receipt"]) AND  
       ("Job No." <> ''))  
   THEN  
    IF (ItemLedgEntry.Quantity < 0) AND  
      (ItemTrackingCode."SN Specific Tracking" OR ItemTrackingCode."Lot Specific Tracking")  
    THEN  
     ERROR(Text018,"Serial No.","Lot No.","Item No.","Variant Code");  

Hope you got the code behind the prevent negative inventory option in Microsoft Dynamics NAV.