Non Realization of Export Invoice Amount(Services)

Dear Sir/Mam

We have a service Invoice export with LUT in the month of Jun'21 due to some issues our client can pay that amount in March'22.. here amount will be realsed after 9 months.. do we need to pay any RCM IGST due to non realization of amount.

if yes if we pay can we get refund later we recieve the payment.