Hello,Professional tax is levied by the state governments on the income of all individuals earning through profession, employment or trade. Every state has its own laws and regulation to govern professional tax of that particular state. Since professional tax is levied by the state government, it tends to differ for various states.Regarding whether you need to fill it in GST registration,If you have professional tax registration, you are required to mention it while filing your application for GST registration, or elseIf you don't have registration at the time of GST registration, then no need to mention it in the application but you need to check whether you are required to get registration according to laws prevailing in your particular state.I hope that this answer satisfies your requirement. For any query, please feel free to write to me at badlaniassociates@gmail.comRegards,CA Hunny BadlaniBadlani & Associates