An Invoice is a commercial document issued by a Seller to a Buyer, indicating the products, quantities and agreed prices for products or services that the Seller has already provided the Buyer with. An Invoice indicates that, unless paid in advance, payment is due by the Buyer to the Seller, according to the agreed terms.

The Invoice usually contains: PO #, Date, Billing Address, Shipping Address, Terms of Payment, List of products with quantites and prices.

Invoices are sometimes called Bills.

If the buyer returns the product, the seller usually issues a Credit Memo for the same or lower amount than the invoice, and then refunds the money to the buyer.

Invoices for hourly services work (such as by lawyers and consultants) often pull data from a timesheet.