Cancellation of Invoice

A small service provider mistakenly issued and paid GST on an invoice in March 2019 for services that were paid for later. They are seeking advice on how to cancel the old invoice and reclaim the GST paid, as they intend to issue a new invoice. While initial advice suggests amendments for FY 2018-19 are no longer possible after September of the following year, there's a suggestion to check the GSTR-1 return amendment table for FY 2018-19, as it might still be active.