Credit note for invoice issued in f.y 2017-18

No. Last date was 30.09.2018.

Sec. 34(2) of CGST Act

"Any registered person who issues a credit note in relation to a supply of goods or services or both shall declare the details of such credit note in the return for the month during which such credit note has been issued but not later than September following the end of the financial year in which such supply was made, or the date of furnishing of the relevant annual return, whichever is earlier, and the tax liability shall be adjusted in such manner as may be prescribed."