A shell corporation or shell company is a company which serves as a vehicle for business transactions without itself having any significant assets or operations. Shell corporations are not in themselves illegal and they may have legitimate business purposes. However, they are a main component of the underground economy, especially those based in tax havens.

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Note added at 14 mins (2009-02-04 19:52:53 GMT)
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An example: Sydney Pollack's film "The Firm" is also known as "La Tapadera" in Spain ...