There is no time limit specified under GST law but section 34(2) indirectly speaks about time limit for issuance of credit note:- Section 34(2) says, "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: Provided that no reduction in output tax liability of the supplier shall be permitted, if the incidence of tax and interest on such supply has been passed on to any other person." Thus time limit for isuance of credit note is Sep or filing of Annual return whichever is earlier.