Discharge the liability of Reverse Charge Mechanism reg.

This discussion concerns a client who settled their Reverse Charge Mechanism (RCM) liability for the 2017-18 period in September and December 2021 via GSTR 3B filings. The query seeks to confirm whether this practice is correct and requests relevant rules, acts, sections, or circulars to support the answer. It also references sections 12(3) and 13(3) of the CGST Act regarding the time of supply for goods and services under RCM.