(1)Subject to the provisions of this section, a deduction of such profits and gains as are derived by an undertaking from the export of articles or things or computer software for a period of ten consecutive assessment years beginning with the assessment year relevant to the previous year in which the undertaking begins to manufacture or produce such articles or things or computer software, as the case may be, shall be allowed from the total income of the assessee:Provided that where in computing the total income of the undertaking for any assessment year, its profits and gains had not been included by application of the provisions of this section as it stood immediately before its substitution by the Finance Act, 2000, the undertaking shall be entitled to deduction referred to in this sub-section only for the unexpired period of the aforesaid ten consecutive assessment years:Provided further that where an undertaking initially located in any free trade zone or export processing zone is subsequently located in a special economic zone by reason of conversion of such free trade zone or export processing zone into a special economic zone, the period of ten consecutive assessment years referred to in this sub-section shall be reckoned from the assessment year relevant to the previous year in which the [undertaking began to manufacture or produce such articles or things or computer software] [ Inserted by Act 26 of 1988, Section 4 (w.e.f. 1.4.1989).][in such free trade zone or export processing zone:] [Substituted by Act 10 of 2000, Section 6, for Section 10-A (w.e.f. 1.4.2001).][* * *] [ Third proviso omitted by Act 14 of 2001, Section 6 (w.e.f. 1.4.2002).][Provided also that for the assessment year beginning on the 1st day of April, 2003, the deduction under this sub-section shall be ninety per cent. of the profits and gains derived by an undertaking from the export of such articles or things or computer software:] [ Inserted by Act 20 of 2002, Section 5 (w.e.f. 1.4.2003).][Provided also that no deduction under this section shall be allowed to any undertaking for the assessment year beginning on the ] [Substituted by Act 10 of 2000, Section 6, for Section 10-A (w.e.f. 1.4.2001).][1st day of April, 2012] [ Substituted by Act 33 of 2009, Section 5, for " 1st day of April, 2011" (w.e.f. 1.4.2009).] and subsequent years.