(1)   Where an assessee invests , at any time before the first day of July, 1991, any amount in the purchase of debentures or negotiable bonds issued by the Government or a corporation owned by the Government and approved by the Central Board of Revenue for the purposes of this section, a credit equal to five per cent of nominal value of such debenture or bond shall be allowed against the tax payable by the assessee in the manner hereinafter provided:

(2)   The amount of the credit admissible under sub-section (1) shall be deducted from the tax payable by the assessee in respect of the income year in which the investment is made and in any subsequent year in which the said investment is retained.

(3)   Where no tax is payable by the assessee in respect of the assessment year relevant to the income year in which such investment was made, or where the amount of the tax payable is less than the amount of the credit, the amount of the credit or so much of it as is in excess thereof, as the case may be, shall be carried forward and deducted in the manner laid down in sub-section (2) from the tax payable by the assessee in the following assessment year and so on, so, however, that the deductions made under sub-section(2) and this sub-section shall not exceed in the aggregate the limits specified in sub-section (1).

(4)   Nothing contained in sub-section (1) shall apply in respect of any debenture or bond-

(a)    sold, transferred or otherwise disposed of by an assessee before the 31st December, in any year; and

(b)    after fifteen years of the date of its issue.

(5)   The provisions of sections 96, 97, 99, 100, 103 and 104 shall, so far as may be, apply to tax credit under this section as they apply to refunds.

(6)   The Central Board of Revenue may make rules regulating the procedure for the grant of approval under this section and any other matter connected with, or incidental to the operation of this section.