This discussion clarifies the amendment rules for GSTR 1 and GSTR 3B. GSTR 3B cannot be amended. While GSTR 1 details can be amended in subsequent months or quarters, there are strict deadlines. For instance, amendments for invoices from FY 2017-18 were only possible until 31st March 2019, meaning such old invoices can no longer be corrected.
➡️ 3b can't be amended. ➡️ Limit details in gstr 1 can be amended, in subsequent month quarter. However, if you want to amend any old invoice belonging to fy 2017-18, you can't now. As last date was 31.03.2019.