Section 37, The Merchant Shipping Act, 2003

(1) Where the tonnage of a ship has been ascertained in accordance with the tonnage regulations and suchtonnage has been assigned to that ship, the tonnage shall be register4d and shall thereafter be deemed to be the tonnage of that ship. (2) The tonnage of a ship ascertained under subsection (1) shall be entered in every subsequent registration of the ship unless— a) an alteration is made in the form or capacity of the ship or b) it is discovered that the tonnage of the ship has been erroneously computed, and in either of these cases the ship shall be remeasured and her tonnage ascertained and registered in accordance with the tonnage regulations.