Resigination

Hi, 

One of my friend submitted resigination on top mnc. He was worked with past  1 year. Suddenly hr call to him please submit resigination because some negative bgv. He also agree because rule is rule rule for all. He submitted resigination. And serving notice period  is also negotiation on notice period. He will get notice period salary also. He will get experience and releving letter and they mention any reason bgv fails??? They have to mention any such type of reasons they have to mention??