When we can claim RCM as ITC

You can claim RCM ITC after the payment of TAX under RCM.

You can claim in the same month in which you are paying RCM, however, you are required to pay RCM through Cash only, You cannot set it off using ITC.

Adding RCM Liability in table 3.1 (d) and adding ITC in table 4A(3) of GSTR-3B. This is make you liable to pay RCM Liability as well as avail the ITC.