what is the purpose of Invoice ?

As we know an invoice or bill is a commercial document issued by a seller to the buyer,

Purpose of invoice is to indicate the products, quantities, and agreed prices for products or services the seller has provided the buyer & to indicate the amount that the buyer must pay the seller, according to the payment terms & the maximum amount of days to pay these goods and are sometimes offered a discount if paid before.

Invoice is documentary evidence of transaction.

thnx PRATEEKKUMAR PATEL