EIM33034 | Seafarers' Earnings Deduction: location of duties performed on ships visiting oil and gas rigs
From HM Revenue & Customs · Employment Income Manual
Drilling rigs positioned in a designated area
Section 41 ITEPA 2003 treats as performed in the United Kingdom any duties performed on a gas or oil rig outside the 12 mile limit but in a designated area of the continental shelf.
Section 382 treats as performed in the United Kingdom any duties performed on voyages or part voyages by ships that either:
start and end in a designated area, or
start in the United Kingdom and end in a designated area, or
start in a designated area and end in the United Kingdom.
This does not affect the test of whether a person is absent from the United Kingdom. If he or she is outside the 12 mile limit at the end of a particular day that day is a day of absence for the purposes of an eligible period, see EIM33004.
Drilling rigs positioned outside of the designated areas
A voyage or part voyage by a ship to a rig while it is drilling outside a designated area is regarded as ending outside the United Kingdom. The return voyage will be one that begins outside the United Kingdom.