How to delete a subcontractor PO

Subcontractor Contracts (Subcontractor POs created through the plan & track section), can only be deleted within the plan & track section of the job they were created under.

First, open the job this subcontractor PO was added to and navigate down to the job phase in Plan&Track where it was added. You'll notice under the subcontractor heading, there will be a clickable link that lists the [PO#___] 

Clicking this link will open a window that shows the original PO amount and gives you the option of editing the subcontract:

After clicking edit, you will have the option to delete: