You can create a Bill (Expense) directly from any object within Salesforce.
To do this, follow the steps below:
The below section refers to Basic Mapping
Enter the details of the header object, child object and related lookup fields. In this case our Bill header object is Opportunity and OpportunityLineItem is our child object.
The below screenshot displays the fields for the line items to be mapped from the selected object
The line object will require product description, quantity, unit price, account code and tax rate.
A Bill can be generated from a single custom object or from an object with a child object. Child object is where your line items are stored.
For ex: Opportunity is a parent object while Opportunity products is a child object
After the mapping is set up, you can create a Bill in one of the following ways: