( 1 ) THE petitioner is a Sanitary Engineer and works as the Sanitary Contractor under the name and style of "m/s. S. C. Bose" at No. 309, Bowbazar Street, Calcutta. In the year 1950 the petitioner filed an application under Section 7 (2) of the Bengal Finance (Sales Tax) Act, 1941 for making himself registered as a registered dealer under the said Act. The petitioner states that the petitioner got himself registered under a mistaken impression that the petitioner was a dealer under the said Act and was liable to pay the tax under the provisions of the said Act and the Rules made thereunder. On that basis the petitioner duly filed returns from 1951 to 1958 and along with the returns paid a sum of Rs. 18,812. 45 p. on account of sales tax. The petitioner states that the same was paid on a mistaken notion of law. As a result of the decision in the case of Dukhineswar Sarkar and Brothers v. Commercial Tax Officer, (1957) 8 STC 478 = (AIR 1957 Cal 238) and the decision of the Supreme Court in the case of State of Madras v. Gannon Dunkerley and Co. (Madras) Ltd. , ft became apparent that the petitioner was not a dealer and the Rule 2 (ii) (c) of the Bengal Sales