In Britain's Crown Dependencies, the Manx pound, Jersey pound, and Guernsey pound are unregulated by the Bank of England and are issued independently. However, they are maintained at a fixed exchange rate by their respective governments, and Bank of England notes have been made legal tender on the islands, forming a sort of one-way de facto currency union. These currencies do not have ISO 4217 codes, so "GBP" is usually used to represent all of them; informal codes are used where the difference is important.