means A written list of goods or services provided, stating the amount owed and the terms for payment.

from From French envoi, meaning 'a sending' or 'something dispatched' — the same root as 'envoy.' An invoice was originally the paper that accompanied dispatched goods, the plural envois softening into the English 'invoice.' So at heart the word simply means 'the things sent' — the polite accounting of what's already on its way to you.