The Ports Act 1991 (Levy on Disposals of Land, etc.) Order 1992

13.  If in the period between the end of any previous disposal period and the end of the disposal period to which the disposal statement relates an amount of levy has pursuant to article 8(3), 8(5) or 19 to 35 become payable in respect of a disposal made or to be regarded as having been made in an earlier disposal period, the disposal statement shall give particulars of how that amount and any interest thereon is computed (including in respect of a disposal on which a gain is regarded as arising by virtue of paragraph (3) of article 8 or paragraph (2) of article 25, the particulars regarding the disposal which would have fallen to be given in the disposal statement for the disposal period in which the disposal took place had the disposal been regarded at the time when that disposal statement was furnished as one on which a gain arose).