A pro forma invoice

Proforma invoice is Abridged or estimated invoice sent by a seller to a buyer in advance of a shipment or delivery of goods. It notes the kind and quantity of goods, their value, and other important information such as weight and transportation charges. Pro forma invoices are commonly used as preliminary invoices with a quotation, or for customs purposes in importation.
Proforma invoices also a documents provided prior to or with a shipment of goods (as for export) that describes the items and terms of sale but does not have the function of a real commercial invoices.

What is a commercial invoice?

An commercial invoice is essentially a detailed bill left by vendors and outside suppliers for goods or services rendered to a company. A typical invoice might list the quantity of each item, prices, billable hours, service description and a contact address for payment. While some expenses may be paid out of a general fund or petty cash account, an invoice is usually paid through an accounts payable department by the posted due date.

An invoice is a legal document which can be used as evidence of an incurred debt. The recipient of the goods or services can challenge the legitimacy of individual charges, but the invoice itself is considered a bona fide debt. Sometimes a vendor or serviceman cannot collect on a bill immediately, so their company will send an invoice at a later date for payment. The actual daily expense of a service may be so low that a company will simply wait for a larger invoice to cover all of the costs at once.