2.The petitioner is a registered dealer under the provisions of the Tamil Nadu General Sales Tax Act (TNGST Act) on the file of the respondent and carrying on works contract of supply, erection and commissioning of generator sets on contract basis. During the assessment year 2005-2006, the petitioner had entered into an agreement with M/s.PSG College of Arts and Science for supply, erection and commissioning of generator sets. The petitioner filed their returns and in respect of the turnover under the works contract, they exercised the option under Section 7C of the TNGST Act and consequently, assessment was completed by order dated 23.10.2007 charging the petitioner to tax at 4%. After about three years, this assessment is sought to be revised by stating that verification of records reveal that the petitioner has effected supply of Genset to various customers and hence taxable at 16% as first sales.