I have done my GST migration as a normal taxpayer and also have an SEZ unit which is my additional place of business. I have declared the same in the enrolment application also. What should I do under GST?

You need to apply for a new registration as separate vertical under GST for your additional place of business i.e. the SEZ unit/ SEZ Developer because SEZ has separate registration requirement under GST. You need to select SEZ Unit or SEZ developer in the reason for registration. You are also required to upload the necessary certificate /documents issued by the Government of India in the principal place of the business tab to substantiate the claim.