RCM U/S 9(3) Scrap Supply

Certain RCM liability for the FY 2017-18 is not paid till date covered u/s 9(3) scrap and waste supply of reverse charge. Now during the course of GST audit, the liability is identified and the client is willing to pay. My question is can we take input of the same in FY 2019-20 or anywhere so input avail. I very well understand that there is a time limit till 31/03/2019 to claim inputs. However this is a different case as my eligibility to claim input arises only upon payment of RCM in cash. I am trying to take a stand that time limit for claiming ITC does not apply to belated tax paid under RCM. Need your inputs. Kindly Suggest what best possible way for it