I have sold goods and submitted the GST return, but the party does not want to make payment and requests for cancellation of this invoice. I have already generated waybill also. Can I do that?

There is no mechanism to cancel the invoice when goods are already delivered and not returned. Further no credit note can be issued in case of non- payment by customer. Section 34 of the CGST Act, 2017 allows issuance of a credit note only in specific three cases (goods return, deficiency, value change) and thus, in case of non-payment by customer, the credit note cannot be issued. Thus, in present case, both options are not available. You should try to recover the value of goods supplied along with GST from the customer.