Definition of an Invoice
An invoice received from a vendor is a billing for goods or services that it had provided. The vendor's invoice will include the quantities of the items provided, brief descriptions, unit prices, amount due, credit terms, where to remit payment, etc.
Definition of a Voucher
A voucher is an internal document used by a company's accounts payable department in order to collect and organize the necessary documentation and approvals before paying a vendor's invoice. The voucher acts as a cover page to which the following will be attached: vendor's invoice, company's purchase order, company's receiving report, and other information needed to further process the vendor's invoice for payment.