ITC Eligibility under RCM - Goods and Services Tax - GST

A registered taxpayer has received services from an unregistered person during FY 2018-19 on which he is liable to pay tax (IGST) under RCM but no invoice was issued at the time of service received and no tax was paid. After being observed by the department in 2023, the RTP raised the invoice and paid the IGST along with interest, and at the same time availed ITC on the tax so paid under RCM on the contention that the date of invoice raised doesn t violate Sec. 16(4) . Is the RTP eligible for the ITC?