Русско-англо-русский юридический словарь

A medium of exchange is an intermediary used in trade to avoid the inconveniences of a pure barter system. A medium of exchange permits the value of goods to be assessed and rendered in terms of the intermediary, most often, a form of money widely accepted to buy any other good. (Wikipedia)

An indirect tax (such as sales tax, a specific tax, value added tax (VAT), or goods and services tax (GST)) is a tax collected by an intermediary (such as a retail store) from the person who bears the ultimate economic burden of the tax (such as the consumer). The intermediary later files a tax return and forwards the tax proceeds to government with the return. In this sense, the term indirect tax is contrasted with a direct tax which is collected directly by government from the persons (legal or natural) on which it is imposed. (Wikipedia)

A diplomatic agent is a national representative. Originally, diplomatic agents helped to work out certain negotiations between nations, but now a diplomatic agent acts as an intermediary of a foreign nation and the nation which employed the diplomatic agent. (definitions.uslegal.com)

Intermediary services: Intermediaries

The term intermediary refers to a person who makes arrangements for, or facilitates, a supply to be made between two other persons. They can provide services to customers who may be either the supplier or the recipient of the supply which is being arranged, or to both. Intermediaries may be referred to as brokers, buying or selling agents or go-betweens. (hmrc.gov.uk)