The Guernsey pound £ is in a currency union with the United Kingdom GBP and all pound sterling notes are accepted wherever they were printed. Guernsey banknotes can be exchanged at par at all banks in the sterling area including the UK but many retailers in England are suspicious of them in the same way they are sceptical of sterling banknotes from Northern Ireland, Scotland and Jersey. Consequently, its less hassle if you make sure you leave with Bank of England notes. ATMs generally describe which currency is being dispensed - 'Local' or 'English'.
Financial services - banking, fund management, insurance, etc. - account for about 55% of total income in this tiny Channel Island economy. Tourism, manufacturing, and horticulture, mainly tomatoes and cut flowers, have been declining. Light tax and death duties make Guernsey a popular tax haven. The evolving economic integration of the EU nations is changing the rules of the game under which Guernsey operates.