Bill Sales Order permission under Permissions tab > Transaction subtab > is not available when editing or creating a new custom role. This is because Advanced Shipping feature is not yet enabled. For more information about this feature, see Advanced Shipping.
To resolve, login as Administrator and follow the steps below.
1. Navigate to Setup > Company > Enable Features.
2. Click Transactions tab.
3. Under Shipping & Receiving section, mark Advanced Shipping.
4. Click Save.