( 1 ) THE petitioner is a company incorporated under the Companies Act and carrying on its business at 20, Maharshi Debendra Road, Calcutta-7. The petitioner is a dealer in iron and steel and registered under the Bengal Finance (Sales Tax) Act, 1941 (hereinafter referred to as the said Act ). For the period of four quarters ending 31st December, 1967, the petitioner was assessed by the Commercial Tax Officer, respondent No. 1, on the 30th September, 1971, under Section 11 (1) of the said Act. In computing the taxable turnover the Commercial Tax Officer rejected the claim made by the petitioner under Section 5 (2) (a) (ii) of the said Act on the basis of the declaration form supplied by the purchasers, the registered dealers. The petitioner claimed exemption of a total amount of Rs. 25,89,286. 18, but the Commercial Tax Officer disallowed Rs. 1,72,905. 62 with respect to sales to M/s. Laxmi Iron and Steel Co. , M/s. Bansal Iron and Steel Engineering, and M/s. Krishna Commercial Engineering on the grounds that purchasing dealers' registration certificates were cancelled on 28th April, 1969, 9th November, 1970, 12th April, 1971, and 25th November, 1970, respe