Negative Stock for back-flushed Parts even Negative Qty action in Part Class is set as Stop.
It’s a standard functionality in Epicor(&other ERP systems). System will try to do back flushing material even though the material is not available in stock.
To avoid this, We have to enable FIFO Layers and in this case System will not allow to consume a material if it’s not available irrespective of what we have mentioned in PartClass Negative Qty Action.
So if you don’t want to issue backflushed material if there is no stock, you can enable the FIFO Layers and stop system making negative transactions.
To enable FIFO Layers, Launch the screen System Setup> Company/Site Maintenance>Site Cost Maintenance and click “Enable FIFO Layers” and your issue will be resolved.