If you operate in a 4PL scenario, you may need to calculate expenses on warehouse operations (Sale Orders, Purchase Orders and Storage).
This allows you to load expense rates and create Bills based on Warehouse Operations. 

Enabling Warehouse Expenses:

From Organisation Settings, head to the "Features & Options" tab.
Then scroll down to the section named "Charges Configuration", and turn on "Enable Warehouse Expense Charges".

Create a Supplier for a Warehouse:

Create a new Supplier (explained here: Suppliers)

Then link the supplier to the Warehouse you want to calculate charges for:

Once you've created the link, it'll be visible:

If you require specific customer-supplier charges, for instance, the Supplier charges different picking or storage charges to your clients, then you can create specific Supplier Rates for Specific Customers

Loading Expenses against Sale Orders, Purchase Orders and Storage Periods

The rates loaded into the Supplier's Charge card for picking, packing and storage are used when calculating the expenses.

In addition, Item Charge Data and Adhoc Charges can be modified independently for both Income and Expense: