Overview
When you place the quantity is more than the Inventory of HMSA, system will generate the backorder for you. And HMSA will deal with the backorder first when HMSA inventory is available.
Backorder - List
Click Order MGT - Backorder to go to Backorder page:

In this page, you can view or cancel the backorder.
Backorder - View
Click View and go to the details page, then you can see the details of this backorder.

Backorder - Cancel
If you don't want to keep waiting for this backorder, you can click Cancel to cancel this backorder.
