You cannot revise the GSTR 1 once filed. However, the month you realise there is an error, you can amend the error of the prior months in the GSTR 1 of the month in which you realise there is an error. For eg: If you have already filed GSTR 1 for Jan and you realise in March that there was an error in Jan - then in the GSTR 1 of March, there is an option to amend the GSTR1 of Jan. Amendments can be made in each invoice and details . Both type of amendments have there own limitations. These must be followed clearly to avoid any mistakes in filing GSTR 1. A. Which filing period to select?- Return filing period must be the period in which amendment is made. For example if amendment is made July and return filing period will be- July if he is required to file monthly returns September if he is required to file quarterly returns i.e. July- September. B. Invoice level Amendments- B2B Amendments B2C Large Amendments Credit/Debit Notes (Registered) Amendments Credi