Just as we prevent deleting Repair Orders, we also prevent deleting a Parts Sale. This is to prevent fraud within the shop.

To change the STATUS of a part sale to "Dead/Refunded", which will remove the Parts Sale from your Main Page (WIP), as well as all reports

First find the Part Sale you are trying to Dead/Refund, either on the WIP screen or in Find RO by selecting the Part Sale feature and searching for the PS number. 

Once a Part Sale is selected, and opened, you'll change that status to 'Dead/Refunded'