All the existing Taxpayer under VAT, Service Tax and Central Excise, you can enroll yourself till next 3 months.
On the registration of businesses, all the subsumed tax assesees, have migrated to the GST Network. Registration, which closed on June 15, will reopen on June 25. The provisional ID number will be the same for GSTIN (GST identification number). New businesses too need not rush. They will have 30 days for GSTIN.