URD purchase in regular scheme

Yes, GST is applicable on Purchases from URD. Since, the recipient is registered under GST, GST is payable under RCM at the rate based on HSN.

You can calculate and pay RCM in the month of purchase under table 3.1 (d) and claim ITC in the same month under table 4 (3), in GSTR 3B.

Also, you are required to issue self invoice for the RCM Inward supply.

However a limit of 5000 is set for exemption, where you are not required to pay RCM. 

Hope this clarifies your doubt. Do contact incase of any difficulty.