Login to Back Office > from the left menu click on ‘Reports’  > click on ‘Sales’ tab  > select shop from ‘Select Store’ drop down > from the next drop down of ‘Select report type’ click on ‘TAX’ > now select ‘GSTR1’ option from the drop down list of ‘Sub Report Type’ > as a last step please select appropriate date range from ‘From To Date’  and click on ‘Submit’ button > ‘Download’ option will appear on screen.

Click on the ‘Download’ button, the report will be generated in excel format.