Reactivation of a Cancelled GST Registration is possible. An application for reversal of cancellation of GST registration can be done by applying under Form GST Reg-21. Within 30days of receiving the cancellation note of GST Registration the application has to be submitted. If a GST officer has cancelled the GST Registration for the reason of non-filing of tax returns, the re-application of GST can only be filed, after the payment of interest and penalty and paying the pending returns. On investigating a re-filing form of GST Registration, if the concerned officer is not satisfied with the revocation application, then a show cause notice is sent in Form GST Reg-23 to the tax payer, elaborating the reason of rejecting the cancellation application. The officer will question the tax payer that why the refusal application should not be rejected. Within 7 working days the applicant should respond from the date of issue of the notice.. The tax payer has to mention the reason for revocation and submit the application on the website. If the officer finds the reasons satisfactory then the GST number will be revoked by the officer. All the formalities can be done online easily by visiting the GST official website.