What are the steps to file nil GSTR- if there were no transactions in a period?

To file nil GSTR-1 when there are no transactions in a period, you have to simply generate gstr1 of a same period from a BUSY & then upload on gst portal.
 For generate GSTR1from BUSY please follow these steps:
 1. Open the BUSY.
 2. Go to the display and click on gst reports option and then click on gst returns and press enter on GSTR1 eReturn
 3. Select the month of which month or period you want to file the return.
 4. Enable / disable the required option according to your requirment
 5. Specify the path for return file like JSON
 6. Click view and generate return file 
 7. Log in to the GST portal.
 8. Go to the Returns section and select GSTR-1.
 9. Choose the tax period for which you want to file the nil return.
 10. Select the option to retrun file which we generate from BUSY. 
 11. Review the summary and confirm that there were no transactions during the period.
 12 Submit the nil return on the GST portal.
 Please note that these steps may vary slightly depending on the specific interface of the GST portal and any updates made to the filing process.