Why can't I unpost a Receiving Ticket?

The Receiving Ticket will lock down and prevent editing weights or amounts after certain conditions have been met. 

1. The Receiving Ticket is in a closed period. You can easily check what the current closed period is by looking at the Company drop down at the top of your screen:

2. An expense has been paid. You can check the Expense tab of the Receiving Ticket to see if anything has been posted. 

3. An inventory item has been committed to a Converting Job, Packed in a container, or pulled onto a Shipping Worksheet. This is regardless of the status of the Shipping Worksheet or Converting Job; if the item is committed, then the Receiving Ticket is locked down.