Each country has different rules of taxation, which could be very confusing for foreign artists. In the UK you have e.g.  specific rules for the withholding of income tax, which means that a certain percentage of the fee is withheld to the Foreign Entertainers Unit.

You can read more about this at FEU's home page.

For a more in-depth walkthrough of the UK tax rules for visiting entertainers, this article is recommended.