Credit note problem

GouTam SachDeva (70 Points)

13 April 2018  

Suppose i issued a credit note to unregistered in MARCH (Original invoice was issued in feb) value 600+18%gst. Place of supply was ASSAM.  No more supply made to Assam in March month.

So how can i adjust this value in gstr3b, how can i claim its tax in 3b