All existing Central Excise and Service Tax assessees will be migrated to GST starting 7th January 2017. To migrate to GST, assessees would be provided a Provisional ID and Password by CBEC.
Provisional IDs would be issued to only those assessees who have a valid PAN associated with their registration. An assessee may not be provided a Provisional ID in the following cases:
a. The PAN associated with the registration is not valid
b. The PAN is registered with State a Tax authority and Provisional ID has been supplied by the said State Tax authority.
c. There are multiple CE/ST registrations on the same PAN in a State. In this case only 1 Provisional ID would be issued for the 1st registration in the alphatebical order provided any of the above 2 conditions are not met.
The assessees need to use this Provisional ID and Password to logon to the GST Common Portal (https://www.gst.gov.in) where they would be required to fill and submit the Form 20 along with necessary supporting documents.
Subsequent pages provide the Steps to be followed by each assessee to migrate to GST.
Source : cbec.gov.in