Good news is that errors, mistakes &  omissions in GSTR-1 is now possible. The same is discussed hereunder:

1.       If any invoices have been skipped to be entered, you can simply enter them in respective columns, along with current month’s invoices, entering the original Invoice dates.

2.      Amendments in B2B : These can be done through Table No. 9A of GSTR-1. You need to select the year FY 2017-18, enter the invoice number, and make appropriate amendments after clicking on ‘Amend Invoice’, under Tab ‘Uploaded by Taxpayer’

3.      Amendments in Exports : These can be done through Table No. 9A of GSTR-1. You need to select the year FY 2017-18, enter the invoice number, and make appropriate amendments after clicking on ‘Amend Invoice’, under Tab ‘Uploaded by Taxpayer.

4.      Amendments in B2C Large : These can be done through Table No. 9A of GSTR-1. You need to select the year FY 2017-18, enter the invoice number, and make appropriate amendments after clicking on ‘Amend Invoice’, under Tab ‘Uploaded by Taxpayer’

5.      Amendments in B2C Small : These can be done through Table No. 10 of GSTR-1. You need to select the year FY 2017-18, enter the relevant month and Original Place of Supply (POS), and make appropriate amendments after clicking on ‘Amend Details’

Kindly note that due date to rectify errors / omissions in GSTR-1 relating to FY 2017-18 is 31st March 2019.

Accordingly.  the registered persons are allowed to rectify the error or omissions made in already filed GSTR-1 for July 2017 to March 2018, till due date for quarter ended January-March 2019 i.e., 30th April, 2019 for those assesses who have opted for quarterly filing of GSTR-1 and till due date for filing GSTR-1 of March 2019 i.e. 11th April, 2019 for other assesses.