Tax treatment of workers in the North Sea and other offshore oil and gas fields: territorial extension of the charge to tax on employment income
Section 1013 ITA 2007
For all income tax purposes, United Kingdom territorial waters, that is, waters within twelve nautical miles of the shore, are treated as being part of the United Kingdom. So earnings for duties performed in territorial waters are classed as earnings for duties performed in the United Kingdom.
Exploration or exploitation activities in a designated area
For the purposes of the charge to tax on employment income only, Section 41 ITEPA 2003 treats general earnings arising from duties performed in a designated area in connection with exploration or exploitation activities as general earnings in respect of duties performed in the United Kingdom.