In FX trading, the mid-market rate is derived from the mid-point between the bid (for a sell order) and ask (for a buy order) transactional rates from global currency markets. A mid-market rate is therefore not usually a transactional rate. This is especially for retail traders or small to medium sized businesses. It is used for price discovery, valuation and accounting purposes. Transactional currency rates include overheads and profit margins that are independently set by foreign exchange providers; their rates can vary a lot and will differ from the mid-market rate.