Missing bills

What if we have missed Purchase bills of Mar-2020. can we consider those purchase bills in May GSTR 3B returns..? 

Could you please explain it in details 

Purchase of goods is neither reported in GSTR3B nor in GSTR1 

However if you have missed to cliam ITC pertaining to purchase of Feb 2020 then you can claim the same in May 2020 GST return.  

Thank you so Much...

@ raver

I have replied as per your first week that you have missed your sale bill