The EU & OECD
European Union
The Isle of Man has a special relationship with the European Union set out in Protocol 3 to the United Kingdom's Treaty of Accession. Under this special relationship, the Island is neither a member state nor an associate member of the European Union. It is also worth emphasising that the Isle of Man is an internally self-governing dependent territory of the Crown and is not part of the UK. Under Protocol 3, the Isle of Man is part of the customs territory of the Union. It follows that there is free movement of industrial and agricultural goods in trade between the Island and the Union.
The Isle of Man neither contributes to, nor receives from, the funds of the European Union, thus guaranteeing the Isle of Man's fiscal independence. Any proposal to change Protocol 3 would require the unanimous approval of all Member States of the Union, including, of course, the UK. Apart from the requirements of the Protocol, in particular that the Isle of Man Authorities shall apply the same treatment to all natural and legal persons of the Union, the other Union rules do not apply. The Island's relationship with the Union allows it to trade with countries in the European Economic Area in a fashion generally similar to its trade with the Union itself.
OECD (Organisation for Economic Co-operation and Development) 
When the OECD Convention (Organisation for Economic Co-operation and Development) was ratified by the United Kingdom in 1961, the territory to which the Convention applied was not specified. After consultation with the Island's Government, on 19th July 1990, the UK clarified its territorial application and confirmed that the OECD Convention also extended 'to certain UK dependencies including the Isle of Man.'
As a consequence of this decision, the Isle of Man has subscribed to certain obligations - the most important are expressed in the twin Codes of Liberalisation of Current Invisible Operations and of Capital Movements and the National Treatment Instrument.
The Codes have the legal status of an OECD decision which is binding on all members. The general principle is that member countries undertake to remove restrictions on specified lists of current invisible operations and capital movements with the ultimate objective that residents of different countries should be as free to transact business with each other as residents of a single state.
The National Treatment Instrument which is currently non binding lays down an obligation that foreign controlled and owned companies should be afforded a standard of treatment equivalent to that accorded to similarly placed domestic firms. By acceding to the Convention, Isle of Man based financial institutions should benefit from improved rights of access to markets and establishments in OECD member states.