If you need to enter an old case, but the inventory has expired in your custody since the case was performed then you'll need to make some modifications.
Locate the inventory you need to add to the case, but which is expired.
Open the detail screen
Copy the expiration date or UDI to a note so you can retrieve it later
Delete the expiration date or UDI if there is one
Save.
Repeat these steps for any other expired items that must be added
Now mark the devices used in the case
Once the devices have been added, but before submitting for billing, click on each device in the Used Devices screen.
Add the UDI or expiration date back to each device, then save.
You should be all set to submit the event for billing.

