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HMRC internal manual

Tonnage Tax Manual

Offshore activities: Types of vessel

Periods of inactivity

The treatment of periods of inactivity when a qualifying ship is neither being utilised on offshore activities nor elsewhere is prescribed by FA00/SCH22/PARA106.

A period between contracts when a qualifying ship is not working shall not be taken to be a period during which the ship is engaged in offshore activity unless:

  • the period of inactivity is specifically related to a forthcoming offshore activity, and
  • it is impractical for the vessel to undertake other work in the meantime.

Both conditions would be satisfied if, for example, a ship were being fitted at a shipyard with special equipment , which was needed for the forthcoming offshore activity.

Therefore, for any ship, each day in an accounting period will be either:

  • an offshore day, when the ship is used for an offshore activity or is being prepared to be so used, and which is not counted in computing any tonnage tax profit, or
  • a tonnage tax day, taken into account in computing a tonnage tax profit.


FA00/SCH22/PARA106 (treatment of periods of inactivity) TTM17606
Different types of vessel and their treatment TTM11100
De minimis activity ignored TTM11140