Credit note for FY 2018-19

For what purpose

1) You can issue a credit note for invoice issued in FY 2018-19, however, tax adjustment will not be allowed to you. Hence, you can only issue commercial credit note without any tax impact.
2) You can issue credit for invoice issued in FY 2020-21 till September, 2021 and if credit note is issued within said time, you can adjust the tax payment made. Hope it clarifies your concerns.

Less gst deposited

Sorry.. didn't got your comment.. can you please elaborate?

Yes it is hold good