Deductions can only be allowed if they were originally included in the gross tonnage:
Master’s and crew’s accommodation.
Steering and anchoring/mooring machinery spaces.
Safety equipment and battery storage spaces.
Workshops and storerooms for maintenance equipment.
Pumprooms and pumping machinery spaces.
Dedicated water ballast tanks (up to 19 per cent of the gross tonnage when added to exempted water ballast capacity and double bottom space).
Deducted spaces must be certified as being in compliance with all regulations (e.g., crew accommodation standards, construction rules, etc.) and reasonable in extent. They must also be permanently marked by a notice stating their purpose.