The Principal Act is amended in Part 24 by inserting the following Chapter after Chapter 3:

"CHAPTER 4 Petroleum production tax

696G. Interpretation and application (Chapter 4)

(1) In this Chapter -

'cumulative field costs', in relation to a relevant period of a company in respect of a taxable field, means the aggregate of field costs -

(a) for that relevant period, and

(b) for any preceding relevant period;

'cumulative field gross revenue', in relation to a relevant period of a company in respect of a taxable field, means the aggregate of the gross revenues -

(a) for that relevant period, and

(b) for any preceding relevant period,

less the aggregate petroleum production tax payable by the company in respect of the same taxable field for all preceding relevant periods;

'eligible expenditure', in relation to a relevant period of a company in respect of a taxable field, means the aggregate of the amounts of -

(a) all expenditure, including exploration and development expenditure wholly and exclusively incurred by the company in the carrying on of petroleum activities for the relevant period in respect of a taxable field,