What is GIR NO.?

its general index  register number.previously used in incometax. now PAN is used instead of it.

GIR NO; MEAN IN FACTORY WHEN MATERIAL RECIVED IN MAIN GATE THEN ABOVE DOCUMENT STAMPED BY SECURITY & MAKE RECORD IN GOODS INWARD REGISTER THAT  INDEX NO IS MADE A GIR NO.  

Can someone explain to me GIR no? Can someone please also explain the purpose of it?