Regarding ITC uploaded in GSTR1 by 2 years late

A taxpayer claimed Input Tax Credit (ITC) in their GSTR-3B in March 2018 based on an invoice received then. However, their supplier only filed the corresponding GSTR-1 in November 2020, leading to departmental notices. The discussion explores eligibility for ITC under current and previous laws, especially concerning the shift to online credit reconciliation via GSTR-2B, and seeks guidance on relevant notifications.