The correction of C Form has to be by the the party issued such C Forms. Also we have a provision of correcting the same thro online, within 6 months of filing the VAT/CST Returns. In Tamil nadu, the party , who issued the C Form, can correct the same, thro online within 6 mths of filing Returns. Options in TNVAT website, go to online forms, then choose, cancel & reissue, and enter the relevent details , so that the mistaken C Form, wil get cancel and upload the correct details thro an Ann IA, where you will be acknowledged thro online ref no. Then the supporting documents , like cancelled C Form, Original invoice Copy alongwith a photo copy , LR copy , etc, has to be submitted to the Assessing Officer, where, the said officer after verifying the documents, will approve thro online for a revised C Form, and subsequently, the party can generate the same, later.