missing purchase entry in the gst return

No need to made any entry..... only made adjustment when you file your GSTR-3B of April by claiming ITC of March month also...

Book your purchase bill in march 18 only, & take the ITC in april 3b
Just prepare reconciliation statement for the same

thanks to all.

Are You missed Your ITC in Previous months...?? 

If Yes... No need to worry about the mistake... 

You can claim the ITC in Your next GSTR 3B return. As per above query You can take ITC in April month GSTR 3B return... 

You ll book your Purchase in the purchased month in Your books of accounts and C/f the ITC to April...