Login to the link given here
Click on VAT registration or CST registration and choose the appropriate circle
New Dealers (who are not registered under the Tamil Nadu General Sales Tax Act,1959) are hereby requested to fill up the form available through the link below and send the filled in application with necessary enclosures including two passport size photographs of applicant, to the Registering Authority of the area in which their Principal Place of Business is situated with sufficiently stamped self addressed envelope after taking printout. Stamped self addressed envelope after taking printout.
Dealers are encouraged to enter the application online and then to take a printout. This online facility is only to speed up the process of application. Status of application may be watched in this site, using your Acknowledgement number Registration Certificate will be dispatched by the Registering Authority.