(1) In this section, "abandonment losses" means so much of a loss in a petroleum trade incurred by a person in a chargeable period as does not exceed the total amount of allowances which -
(a) are to be made to the person for that chargeable period under this section, and
(b) have been taken into account in determining the amount of that loss in the petroleum trade.
(2) Subject to subsections (5) to (9), where in a chargeable period a person, who is or has been carrying on in relation to a relevant field or a part of it petroleum extraction activities other than effecting the initial treatment and storage of petroleum that is won from the relevant field, incurs abandonment expenditure (not being expenditure which has been or is to be met directly or indirectly by any other person) in relation to the field or the part of it, as the case may be, there shall be made to the person for the chargeable period an allowance equal to the amount of the expenditure.
(a) Subject to paragraph (b
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