All Taxable Goods and Services when received from Unregistered Dealer then Receipient will pay Tax Under RCM basis as per the Supplies Rate...
The RCM is applicable two sections under CGST act like 9(3) and 9(4)**
Now, In current scenario
Sec 9(4) is Suspended from 13th October 17 to 30th September 19.
Sec 9(3) is still applicable. see the details u/s 9(3) related activities in this link https://www.caclubindia.com/share_files/reverse-charge-activities-under-sec-9-3-by-cbec-74794.asp