cash discount

as per section 15 Cgst act

3] The value of the supply shall not include any discount which is given--

[a] before or at the time of the supply if such discount has been duly recorded in the invoice issued in respect of such supply; and

[b] after the supply has been effected, if-

[i] such discount is established in terms of an agreement entered into at or before the time of such supply and specifically linked to relevant invoices; and

[ii] input tax credit as is attributable to the discount on the basis of document issued by the supplier has been reversed by the recipient of the supply.

normally you dont have to reverse itc for cash discount . bevause your vendor will not issue any GST credit note