An invoice is not the same as a receipt
An invoice is not the same as a receipt although both are commercial documents. An official receipt is evidence that payment has been received by the seller while an invoice is a bill or a list of items delivered or received by the buyer for which payment has not yet been received by the seller.
Both receipts and invoices can be used to track inventory and their contents can be similar or identical. The invoice, however includes payment terms and the date payment or payments are due, discount for early payment or charges for late payment.