(1) Where an assessee, being an Indian company or a person (other than a company) who is resident in India, incurs, after the 31st day of March, 1970, any expenditure specified in sub-section (2),
- before the commencement of his business, or
- after the commencement of his business, in connection with the extension of his undertaking or in connection with his setting up a new unit,
the assessee shall, in accordance with and subject to the provisions of this section, be allowed a deduction of an amount equal to one-tenth of such expenditure for each of the ten successive previous years beginning with the previous year in which the business commences or, as the case may be, the previous year in which the extension of the undertaking is completed or the new unit commences production or operation:
Provided that where an assessee incurs after the 31st day of March, 1998, any expenditure specified in sub-section (2), the provisions of this sub-section shall have effect as if for the words "an amount equal to one-tenth of such expenditure for each of the ten successive previous years", the words "an amount equal to one-fifth of such expenditure for each of the five successive previous years" had been substituted.
(2) The