(2) Where for any assessment year any loss computed in respect of a speculation business has not been wholly set off under sub-section (1), so much of the loss as is not so set off or the whole loss where the assessee had no income from any other speculation business, shall, subject to the other provisions of this Chapter, be carried forward to the following assessment year, and—

 (i)  it shall be set off against the profits and gains, if any, of any speculation business carried on by him assessable for that assessment year; and

(ii)  if the loss cannot be wholly so set off, the amount of loss not so set off shall be carried forward to the following assessment year and so on.

(3) In respect of allowance on account of depreciation or capital expenditure on scientific research, the provisions of sub-section (2) of section 72 shall apply in relation to speculation business as they apply in relation to any other business.

(4) No loss shall be carried forward under this section for more than four assessment years immediately succeeding the assessment year for which the loss was first computed.

Explanation.—Where any part of the business of a company (other than a company whose gross total income consists mainly of income which is chargeable under the heads "Interest on securities", "Income from house property", "Capital gains" and "Income from other sources", or a company the principal business of which is the business of trading in shares or banking or the granting of loans and advances) consists in the purchase and sale of shares of other companies, such company shall, for the purposes of this section, be deemed to be carrying on a speculation business to the extent to which the business consists of the purchase and sale of such shares.