As per gst act 2017, if recipient do not made the payment with in 180 days than he is liable to pay interest @ 18%, and reverse the ITC claim.
if supplier pay the tax amount on above transaction than he can issue the credit note to recipient. Reduce the output tax amount from next month output liabilities
As per the Second Proviso to Section 16(2) of the CGST Act 2017, if the Recipient fails to pay the consideration to the Supplier within a period of 180 days from the date of issuing invoice by the supplier, then the Recipient needs to reverse the ITC availed along with interest @ 18% and add to his Output Tax Liability.
Once he pays the entire consideration to the Supplier, then only he will be eligible to reclaim the ITC. But the Interest portion becomes his COST.