Wrongly raised IGST invoice against LUT without tax under the assumption the customer is in SEZ from 2017-18 to Sep 2019. Identified the mistake and corrected by raising credit note for the IGST invoices without tax and issuing fresh GST invoice with tax and uploaded in GSTIN for current year only. Can we make the same correction for 2017-18 and 2018-19? Is there any legal issues by doing so? Is there any time limit for Debit Note for availing input tax credit for the Customer?