Sch 15 para 7
The “transferred proportion” of the net cost amount is the proportion of the decommissioning costs for the TTH oil field that, under the qualifying decommissioning security agreement for the purposes of which the appropriate DSA estimate is approved, is allocated to— (a) the seller, in the case of an agreement entered into before the sale of the interest in the UK oil licence concerned, or (b) the purchaser, in the case of an agreement entered into on or after that date.