Hallo we're running Odoo v8 with Sales, Analytic Accounting/Contract Management and HR Expenses.

How could we distinguish if a sale invoice is a expense invoice or a normal invoice?

I mean, without checking the listed products, from which elements can I infer if it's invoicing expenses to the customer or just invoicing products and services? I'm referring to invoices created from "Invoice" link in the Contract form, beside "Has expenses" column.